An 11X6 is a relativly heavy load for an old 40FP. The FP's were the low priced predasessor to the LA's with deliberately detuned port timing and and smaller venturi for better fuel draw and user friendliness.

My recommendation personally if you want a to try an eleven inch would be to start with a 11x4 maybe and 11/5 but that to may be a bit of a stretch.

Also yes of course do experiment, its good to start acquiring a small selection of props for this and future projects anyway.

John