Hi maurice. The FP is a very nice engine. You also could use it in UC just screwing on all the rotor stop screw until the carb rotor stay all opened. This way it will run like a UC engine and also, you could retrofit it to RC use anytime you want. The Venturi from the OS 40/46 LA-s is exactly the same if you intend to use it on your FP.
The RC and UC version from this engines are absolutely identical, just the carb is different, and in some later motors, OS made a smaller muffler for their 35 and 40 FP, to satisfy the stunt community (OS 762 "S")..