Hi Mark, I currently fly an Ercoupe with a C-85 since my Flybaby isn't finished yet. I have used a McCauley CM7149 and a CM7151 prop with fairly good results. The 49 inch pitch was the best compromise between cruise and climb performance. I'm not sure how the Flybaby ground clearance compares to the Ercoupe though. The 71" diameter prop gives me a little over 6" of clearance from the blade tip to the ground and I don't think you want any less than that. On the Flybaby you would want to check the clearance from blade tip to the ground with the tail raised to flight attitude. Any prop used for a C-85 equipped plane should work if you can find one with the diameter you need. Hope this helps. Ed Exley (eexley@aol.com)