Paul before I ever did any training with an smb I had seen this video and read on here and other forums how to safly deploy an smb.
I can now as far as im concerned safly inflate one. i also only fill it enough to get it on its way. Im normally deep enough so that the air will expand enough so that once on the surface it will be fully inflated.
My old buddy had a self inflating type, he also used to only put enough air in to get it on its way up.
I normally inflate my one by using the bubbles from my exaust on my reg im breathing.
Iv done this over several dives and not had no worries. Im sure other people do things slightly different.
It makes me cringe when I see people inflate one almost full and rise several meters before they actually let the thing go
Simon yes I belive it is a bolt snap, this also stops the line coming undone in your pocket. I find it a bit of a pain as it does sometimes unclip
im currently trying new methods to improve this for my personel tasts.
hth
Jamie