Re-bonding my rabbits and how can i tell who is the boss?

Hi I have two beautiful house rabbits called Betty and Reg. Betty is lion head 1 yr neutered female and Reg is otter Rex 9 month neutered male. I had Betty first and then adopted Reg just after Xmas from RSPCA. they bonded well but then Reg had accident (he thinks he is a mountain goat) and broke his leg. He had big op and after Betty hated him. Vet said this is due to him being seen by her as a threat because he is weak and therefore a danger to her. That was two months ago I have been trying to reintroduce them gently for past couple of weeks they seem ok grooming eachother then all of a sudden start trying to hump each other which then leads to fight. If Betty is ignoring him he will bite her bum, which unsurprisingly she is not so happy about! How can u tell who is boss? Betty grooms Reg much more than he does her ( like humans!) but he copies her and follows her. Hints and tips much appreciated as I would like to know when it's safe to let them share same hutch. Thank you Kate

CAn you tell us a bit more about where you are bonding them, is it a place where either or both have been before? What have you done to neutralise this space? How big is the space? When you say that they fight what actually happens?