That would put you in the most unpopular OPEN class available. The biggest lobbying group that pushed for a .40+ class is now 70+% SSC and on their way to promoting open A using the same equipment with just an engine change that will output the Barrel Horsepower that rivals the LA40.

How does this differ so much from what you want? Well flight envelope and speed won't be all that much, but with a max of 2 1/2lbs the impact distruction they hope to go down from their now defunct C class days. This state in the union loves speed and is home of the fastest combat crowd I've ever been up against.........

I suggest if you want to use a .40 size engine that you reduce the speed by requiring a stock muffler and a common prop and a max allowed nitro or common fuel, I would suggest a 10X3, Master Airscrew and 10% nitro. If someones engines seemed to be handicapped as you get to know each others equipment you could then allow them more nitro content.

Once again learn from others mistakes, the majority will need time to evolve their building and flying skills and are subject to the fast learners with money to spend and what you end up with is a lopsided massacre that is no fun for the majority, only the minority.

Ill list in order what fundamentals, I think kills most combat at the local level, others please chime in with what you think is the priortiy, perhaps some will see a pattern.

Speed, Weight, Funds for constant change, Pilot building skills to be competative.