The head threads of the Ap Wasp are the same as Cox and Norvel. Any head or plug that will fit them will also fit the AP. I have standardized on the Merlin plug and retainer. Cheap and very effective. On some engines, you may need an extra head gasket. If you are running high nitro, that is a given.
My setup is the AP Wasp, Holuszko venturi, Merlin plug, APC 5.5x2.5 prop, and 10,11,11 fuel. Rpm on the ground is around 21K. Lap times on 46' lines is 4.5 seconds. With either a uniflo hard tank (best) or floppy balloon tank, I can do the pattern on 3/4 ounce (25cc) of fuel. The Sky Sport has a 180 sq.in. wing and weighs 9.5 ounces.
Antone Kephart runs backplate pressure and 25% Nitro. He uses an APC 6x2 prop, turning about 23K on the ground. His model is a Baby Magician with 230 sq.in area. Lap times are at 5 seconds on 50' lines. He has a harder time getting perfect runs due to the more critical setup. When it all works, he is unbeatable. (Except, perhaps by Stan Tyler's twin Flite Streak with Medallion .049s, but he has even more trouble with reliability)
Give me reliable power, and I will design or select a plane to suit! I don't need the hassle of variable engine runs. My old motto for 1/2A competition was " He who gets a good engine run wins!" That has proven to be true, even now that we have a pretty good handle on small engines.