how to fatten up a emaciated BP

I recently got a BP that had been rather neglected. He had a nasty belly burn and multable layres of old shed stuck to him. Now he is cleaned up, healing, and just got through a shed that went pretty well all things considered. Now that I have his imediate issues under contol Ineed to fatten him up. Sampson is an adult male that is nearing full growth. When we got him he had been of his food for at least a month, his neck looked sunken and hte skin was loose causnig issues with his neck sheds. He is now eating well. We have him on 1 large mouse every five days. We did sart wth smaller mice and work our way up (this last one he accually had t work a little to swallow) through 5 feedings now. We had a few issues at first due to impacted eye capps but now he's striking like a champ. After he eats he only hides for a few hours before he's out and about again. By the next day he is flicking his tounge out and climbing the side of the take we get him out of, and is just generally very active and inquisitive. By day 3 he is rarly lounging any more at all and stays coiled up on top of his hide (his prefered hunting spot) when he isn't roaming the tank. I don't want to over feed him, but he is still far too skinny. would it be OK for me to try feeding him at this point or should wait? I'm reasonablely sure he'd eat but given his history would it make his tummy sick?

I would say try 2 mice at one feeding, rather than feeding more often. If he won't take 2, then try more frequent offerings. Since he has a few meals in him already he should be ok with whatever he can handle. And do you have an idea of his weight and size? Might even be a good idea to move to rats at this point.

I would definitely convert him to rats. Offer one the same size as the mice he's been getting - it will probably be a weanling rat. If he does ok with it he could be bumped up to a small rat weekly.

I have a couple of concerns about switching to rats, the biggest being that he is nealy full grown (right aroudg the 3 ft mark) and has never had a rat, so I understand it can be difficult to make the switch. He is still on the mend so I want to keep him as well fed as possible and am afraid to risk a hunger strike at this point. The other is a size issue, this (I am told) again comes back to the fact that he has always had mice, he accually struggles a bit to swollow the really big mice due to an exremy skinny neck. He will carry them over to his water dish and dip them first so they go down easier. It's rather interesting to watch. This issue became a bit moot as he started shedding again sortly after Iposted. He's beena week now w/o food, I AM considering trying a small rat to see what he does with it. So, to that end, could anyone tell me if he doesnt like it can yo usually feed him a mouse, or can it put them of eating fr a while?

I would switch him now, while he's still hungry and more likely to switch easily. You don't have to give him an adult small rat if you think that's too big for your snake, a weanling rat is the same size as an adult mouse.

Might be easier to switch now.
Take it slow if he is in as bad of shape as you say.
I would get a pup instead of a small.