mrgoodarmbar,
So how do you do it then since I'm a relatively small guy too? You and shen are my internet coaches. :)
I cross the f@ck out of my ankles.
shen -Siciliano - Thanks so much. Things are much clearer.
Can you guys help me out re my question when you're in someone's closed guard? Do you stay on the balls of your feet or on your feet's knuckles? I'll be asking my instructors this question tom but I appreciate all your inputs.
GRacias.
When sitting in someone's guard, if your INSTEP is on the ground, your center of gravity is lower and more balanced and less "forward" than if sitting with the ball of the foot, BUT some people can't do it due to flexibility.
Some people develop the truly strange habit of being on the knuckles of their curled-up toes and not the flat of their instep or on the balls of their feet.
Literally, on Wed there was a Brown Belt in class who I just noticed did this. I gave him crap about it but he told me doesn't feel comfortable the other way. So do what works for you.
Smaller guys who like to "pop up" to both feet when in the guard will often have the balls of their feet on the ground when they are kneeling. This makes it possible to pop-up more quickly than if you sit with the instep flat on the ground, BUT it also raises your center of gravity and tilts your upper body forward making you -theoretically- more unstable.
interesting...I've noticed that when I am on my insteps my upper body tends to be more forward than when I am on the balls of my feet. being on the balls of my feet has also helped me to not get broken down as easily. I've never had too much trouble with my center of gravity (ie going for a ride ) even though I'm a lighter guy for whatever reason so this hasn't been an issue for me with being on the balls of my feet.
also, Traven teaches a lot of standing passes so I guess that jives with what you were saying Shen.
Every choice we make in BJJ is trade-off whether we realize it or not. Every grip we take, every positioning change makes some things more probable and other things less probable.
Sometimes it is the old trade-off between stability and mobility, other times it is a trade off that you want to prevent "X" at all costs, even if it makes "Y" more likely.
When people say ALWAYS do this or NEVER do that, you really have to take it with a grain of salt. Jiu-jitsu is more complicated than that.
I guess it's OK to tell beginners "never" do this or "always" that, as a starting point, but the longer we do Jiu jitsu we realize there are innumerable exceptions and different ways to do everything. Little in BJJ is categorically "wrong". As long as you are aware of the consequences of any action you take and can handle it, then a move is fine.
So you can't really say "always" or "never" have the instep flat on the ground, or "always/never" cross your ankles.
"Always" & "never" are not very good words to use in Jiu-jitsu.
Instead, we should try to figure out the variables; what happen when I do this vs. what happens when I do that.
People tend to get a little dogmatic about what works for THEM, but that doesn't mean that always is the best way for everyone. People ARE different.
Remember, the advice given by some of the BEST BJJ teachers and champions in the world flat-out contradicts each-other all the time.
That's just the way BJJ is.
Sir Taps - You can cross your feet when armbarring from top if your feet can go underneath the far shoulder. That way both arms are trapped and you've locked in the opp's upper body. Leao Teixeira teaches that there's 3 lines of control in the body - the knees, the hips, and the shoulders. In this case, you're dominating the line of the shoulders.
James
yep
Sir Taps,
Can you explain the knee, hips and shoulders please? To the best of your ability.
I've been taught never crossed the legs from your back because it doesn't allow you to drive your opponent down and you'll get stacked. However, switching from a triangle to armbar you can cross your feet. 
Somebody forgot to tell this guy that you never cross your ankles while doing an armbar.
http://www.youtube.com/watch?v=fNimqv4i8HI
Siciliano - Sir Taps, Can you explain the knee, hips and shoulders please? To the best of your ability.
I can, but badly! Watch this instead, it's Leao Teixeira himself teaching a guard pass that uses this principle. The whole video's great, but skip to 5:19 if you want to see the guard pass.
James
Good thread, Siciliano. I've been wondering lately about when to be on the instep versus when to be on the balls of the feet.
Shen mentioned the stability/mobility tradeoff and this is something I vaguely recall reading or hearing a few years back.
However it was more in the form of defensive (instep) versus offensive (balls).
I'm sure this person also said the same concept was applicable when in side control. My memory of this is fuzzy, though.
It's not a static position, sometimes they cross, sometimes they don't, sometimes it changes.
Sir Taps,
While the video didn't answer my question on where to sit when you're inside closed guard on both knees,those explanations were pure gold.
Wow!!!! Never freaking though of it that way. Those concepts will translate into a hundred possibilites when passing guard. Thanks a million dude.
Siciliano - Yeah, it's a great cooncept. Once you understand it, you can see it everywhere. I was just watching this vid by Franjinha, and although he's not specifically mentioning those lines, you can see that he's controlling 2 lines - line of the hips, and line of the shoulders.
James
James
For later. 
Sub
Sir Taps - You can cross your feet when armbarring from top if your feet can go underneath the far shoulder. That way both arms are trapped and you've locked in the opp's upper body. Leao Teixeira teaches that there's 3 lines of control in the body - the knees, the hips, and the shoulders. In this case, you're dominating the line of the shoulders.
James
one of the most valuable lessomns i topk the time i trained with him aboout lines of control.one
Stupid phone. Best lesson i took from him the one time i trained with him. It was an "ahh" moment.
Say what
Prior to this thread, I didn't even know Leao Teixeira existed. Those of you who have trained with hm are so lucky. Seems like a real gem.
Morgz -Siciliano - 7. "Crossing your ankles for an armbar" - Last night we were taught an armbar setup from mount. Instructor made a really good point that the leg nearestthe head should be the bottom foot when you cross it to avoid the armbar escape.
My question is: When do you cross and when do you not cross the feet?
thanks in advance.
I've been taught that it's ok to cross your legs for arm bar from top (mount), but NEVER cross legs when arm barring from bottom (guard). This is to help keep your opponent's posture broken down when arm barring from bottom (you have more downward torque with your legs uncrossed.
If someone is stacking you from armbar from guard you can cross your feet and spread your knees apart to stop the stack.
The "never cross your feet" thing is more for beginners who lack the sensitivity and experience to know when to cross an when not, since you can always do an armlock with the feet not crossed and only sometimes it's good to cross.