Whats gotten me a 3 way hook up but not the belt was playing a lil truth or dare...you'd be surprised the things you can pull of with a lil t or d
Try getting a sexually charged energy in the room, see if you can get them to kiss, use that to gauge how open they are to fooling with each other, get some heat going on between them
another idea is also playing spin the bottle all together, get your friend to initiate the game (if its you the hb7 thats into you might get slightly offended) Also if you have to kiss the HB9 you can see how the hb7 will react (in terms of jealousy)
Those are the best things I can think of for a greedy cat like you, good luck!