"What weight gloves do you suggest? Do you need big gloves if you've got boxing headgear?"
Tell you the truth i think 12 oz is enough and wearing headgear is gonna make you hit the other guy harder and it's a pain to wear ;) that's not the politically correct answer, which would be: 16 oz gloves and still wear headgear to prevent (even with 16 oz) cuts and swelling.
"What was hard about it?"
Getting hit in the head a lot was hard, and making the nose stop bleeding was kind of a hassle as well, haha.
"I have a very good sense how to dose my force from that time."
"I don't understand. Are you talking about being able to control the amount of force you use when you smack your training partner?"
Yes that's it, we had a very heavy emphasis on technique and control, you know, stop 1 inch from the others face while moving etc. I don't do any of those drills anymore but I still feel that "control" when i spar/train. Especially since I spar a lot with teenagers and children in my class (which is more like play instead of fighting) it's very useful :)
"At least once a week I do a session on the heavy bag or focus mitts specifically for this purpose - get the delivery right. Then get the delivery fast. Then hit stuff hard."
I wasn't referring specifically to you when i said that, just in general and for your training partners since your post sounded like you know what you need but were looking for ideas and opinions.
"Agreed. I've seen it happen - you can't experiment (unless you are an idiot) when there's a chance you'll get busted in the head."
Yeah, sadly some people don't understand that, got such a case in my circle of friends atm... unfortunate and unhealthy mindset.
Sparring is a delicate thing and a lot of it is about trust and not being an asshole, nasty things can happen and ruin your day, bad experiences come 99% from ego and hurt pride, seen it all. I personally don't place such a heavy emphasis on Sparring, it's essential but not more important than any other part of the training.