<<snip>>Someone told me the .46 is not that much more powerful than the .40. I have 10 x6 and 10 x 7 props I could switch out to on the .40. Shouldn't the .40 get the plane in the air on a decent short grass runway?
<<snip>>
You're running an 11X6 on a .40? I'd recommend that prop for the .46, but not for the .40. I think the .40 would be more suited to a 10x6.
If that doesn't get your plane off the ground, try the .46 with the 11X6. The .40 Magnums I've seen were less powerful than the .46's.
Good luck,
Dave Olson