I am now Prop shopping for my RV-9 13B with the 2.85 RD1-C and am leaning towards a Craig Catto prop.  Craig has recommended a 3 bladed prop 70" X 88".  He says that a 2 bladed 76"X 88" prop would have to be 7 inches wide at the root and 3.5 inches wide at the tip, the three bladed prop would have a thiner look to it.  Three bladed prop looks good sitting on the ramp, but nobody sees the prop when it is spinning.  Ground clearance might be a problem with the 76" prop.  Not sure, I have not taken a measurement on this as yet.