90% PPS means you highly relies on the ads network instead of premium sales. If your revenue from ads network is unstable, the PPS rate should be adjusted. How can you survive when you can get only 10% from premium sales and the ads network decreases rates again and again? I cannot understand the logic. At least you should take 40% ~ 50%. You also need to allocate some ratio to webmaster earnings. It can help you make a deal with admins of big forums.