RE: MVVS 15 diesel DFSR-RC
An other thought looking at instruction sheets that come with the engines PAW states up to a 10x6 on the 15==Davis 10x7 on 15 conversion
guess it boils down to what works best in the range "in the air" lots of variables
on the MVVS 15 diesel 15/14 mm bore/stroke just a bit oversquare so not a classic design which are long stroke engines the only thing it shares with the classics is the contra in the bore not the head this would explain the smaller diameter props at least my thought martin