Yes to the bigger sump. There is no evidence that the "head drain" actually does anything. If you are still at the building stage drill out and relieve the oil returns and drill and tap one or more holes as high as possible for sump breathers (running to a catch can, not the head. 8,500 is a lot for an RB30 - they can be made to rev to 10,000 but even at 8500 you will need a quality damper and everything well blueprinted and balanced.