This is only a guess, but I might say part of the increase in flight time might be due to less turbulent airflow over the wings/stab because the propwash goes entirely behind the plane. For a similar reason, reduced p-factor may mean that there is not as severe of a bank angle in the beginning of the flight as you might expect with a tractor config (although most of the time the "torque spiral of death" this year is caused by flexy motor sticks). Additionally, you now have a bit of real estate in the front of the plane to work with a mechanism that may increase the durability of the plane regarding ceiling hits and whatnot, since we had a few issues this year with the ikara props and the prop mount/bearing breaking on ceiling hits (very rare, but still happened).besides increased times, what design benefits would a pusher provide?I ran out of time to test a pusher this year. The weights are high enough that you could do one without sacrificing rigidity. With the tandems we've got, sliding the CG further aft with a pusher might have actually been the optimum solution.Would be cool to see a pusher plane again..
As for preparing for the rules, well, expect the unexpected. Your best bet is to fly AMA classes and push them as hard as possible. Start with a P-18 kit from Lasercut or one of the advanced indoor kits from other vendors (shameless plug) and step things up a notch. Once you can hit 7-8 minutes with a LPP in a gym, you can challenge anyone at Wright Stuff.
edit: and how does/would it provide a benefit?
I don't quite know the feasibility of a pusher plane in kit form, however, as the standard ikara prop would have to be changed to match a pusher config (for those of us that don't make our own balsa props) and/or would require winding backwards (again, depending on the config of the prop) due to the standard flight orientation (turning left circles vs. right circles).