I agree with CP, add a Jett muffler to a .45 and gain more power. Be sure to talk to Dub Jett and explain what you are trying to do and the 16,000 rpm limit. He would also know which sport motors work best with his tuned mufflers. I changed out a stock muffler on a ST .40 some years back and picked up about 1500 rpm on the same prop, which is a lot more power.
Since you are writing the rules, I'd dump the RPM limit and I would also raise the voltage allowed for the airborne receiver pack. Some 2.4 systems work much better with two cell lipo battery packs with a regulator.
Now if the goal is to control speed, the easiest method is to add drag, not weight. A flat plate of plywood or aluminum can limit speeds easily. Since you have tight turns at speed, adding a pound of weight is a easy way to fold wings in a turn, especially if the event is flown on a gusty day. I don't see any restrictions on the airframe. The standard AMA quickie for 426 or 424 pylon racing would do well in your event, and easy since ARF's are available. It might help turnout if you just spec'ed a quickie design as standard. Otherwise a high aspect high wing design with a 10% airfoil would be very good for both the climb and tight turns of the speed course.
I forgot to add:
To get the most laps, you have to design the flight path based on the wind conditions. If the wind is aligned with the course, climb when going downwind, dive into the wind. Much of the altitude change can be done in the turns with little loss of speed (you will be pulling 25 to 35 g's anyway, +/-1 more makes no difference). If you want to read up on it try to find a paper that Jimmy Doolittle wrote on the subject around 1928 or after he received his PhD in Aeronautics at MIT. This is the same guy that planned and flew the B-25 raid on Tokyo and flew the Gee Bee R1 racer that killed everybody else that flew it.
Last edited by HighPlains; 04-30-2014 at 02:33 PM.