Frank,
I think for the MVVS 1.5 would start with a 7x6 wide blade, for the 2.0 something like an 8 1/2x6. For the Irving 20 like a 9x6, the 40's can turn a good prop, wide blade 11x7. The same for the FP convert.

Make sure you have fuel with enough ether in the fuel, the FP Davis Convert can be very sensitive to the  amount of ether. You want to have at least 33% ether to keep temperature control (I have one and with low ether I could not back off the compression to keep steady running).

Best,    DennisT