Most of the older fast designs would be usable in 70mph speed limit combat running Stunt .35's.

I got a stack of plans and non-airworthy old planes I'm slowly working through building or using as templates to build a new one from.

I sent a little crazy with the Berryman Twister and made it for the old rear rotor ST G40. I got two on hand; one new the other warmed up by George Aldrich. Haven't flown it yet, but It should be a rocket with either of them. The new G40 has about 45 minutes on it with 75/25 FAI fuel and is still quite tight, but shows a lot of promise with an 8x8. The Twister should be a good demo plane capable of near 120mph with that engine.