The speed straightaway for rc boat hydros and monos are run according engine size.. It dosnt matter what the engine is pulling to do the speed. The only restriction is the displacement of the engine.. You have in the nitro classes 20, 40, 60, and 90 to1.8 classes gas is 2.6 and 3.5cc. With planes gas can be broader because of the variety size availabe, and nitro as well.... I wouldnt put planes in classes according to body style your talking speed and looking for proformance and creative in the area of speed it self?