Maybe SBR could offer insurance for it's A rated sponsor books, the banner ad books at the top. Play at one of those books and never worry about not getting paid, guaranteed by SBR. I think Russ over at MW used to insure up to$1,500.00 a week a while back at the sponsor books but eventually stopped doing it.
Perhaps the lower tiered books, mostly B rated books could be guaranteed up to 50% of the deposit. C rated, 25% and so on.
This would encorage play at the mid tier books which your sponsors would enjoy and so would your players. Honestly, I would like to try out a lot of your B books but won't do it because I don'y know if I would get paid.
Just a thought guys.