Your rules are pretty good, one exception, they still allow left hand crankshafts, which gives the hard core cutthroat with a machine chop or big money all he needs to dominate the event - and they do! The left hand crank can end up costing more than the engine, throttle, bellcrank, and handle combined.
In the early 1980's, FAI Combat was won by Cox Conquests, Rossis, and of course, The Nelson. In 1988, the 10% nitro/7 mm venturi rule came in and crippled these engines. In 1990, the muffler rule administered the coupe de grass to ALL existing combat 15's. About 50 to 60 combat flyers get stuck about a dozen or more engines each with no event to fly 'em in. As far as I'm concerned, 15 Carrier engines cost nothing. Don't bother with Ebay, just find your local F2D flyer.
Throttles are free, too. Just dip into that box of throttles you pulled off OS's for stunt, racing, and speed limit combat. Adapter, no problemo. Bore out an old venturi so the throttle fits and glue it in with JB or some such thing.
Once the 70 MPH high is in hand, the real fun starts - trying to get a high powered engine to run through the low speed. It's a compromise. Don't be so sure you've got it made in the shade if you bag a Nelson.