Iraqvet, while these guys are bickering, I'd just like to add that I have repropped several trainers owned by students of mine with FP 40s and LA .40/.46s to achieve exactly what you want to achieve: to recap, take off performance and touch and go climbout.

The FP .40 and the LA series of engines seem to be happiest propped on the ground to turn at about 11,000 -12,000 rpm. Obviously, if take off thrust is important, we should get the largest diameter prop onto the trainer that the FP .40 can spin at those rpm levels. All prop loadings and rpm levels being equal, an 11 inch prop will almost always produce more thrust than a 10 incher. You will definitely see the difference when flying them back to back.

The APC 11x4 will probably do at least 12K; the APC 11x5, probably about 11,500 or so (very rough rpm estimations here). The MA 11x6 is a much lighter loading prop than the APC 11x6, and it should spin at maybe 10.5 - 11K on the FP (BB .46 engines pull over 13k with this prop), so it's at the high end of a recommended prop load. An APC 11x6 is probably too much of a load for the .40 and .46 bushing engines.

So in summary, get a few MA or APC props from 11x4 thru 11x6 and try them out.