the more blades the less efficient
the only advantage of a multi blade props is less noise due to a lower tip speed
beter down line - more drag
more clearance
all at the expense of efficiency
full scale go to multi blades to add ground clearence and to help reduce the tip speed from going supesonic
you can start by droping one inch on the 3 blade as a start
the one thing I do like about a three blade prop is they are easy to ballance

hope this helps
Joe