One thing you might want to consider is upsells and cross sells. Give yourself some other ways to make money on your surfers, and when you've had that going for a while you may be able to take out of that to pay a bit more to affiliates so you can offer a more attractive percentage.
Some surfers will buy DVDs but not porn memberships, some will buy memberships but not pay per minute for live shows...if you're only offering one way for them to spend money you're losing out on something.
