I've not used the CD myself but it sounds like a good option to me. The low profile head should fit nicely. Being 1:1 gear ratio, there should be no problem with prop ground clearance. The open cowl design of the 4 * will provide plenty of cooling. Have you done a breakin yet? I've read reports that the CD engines put a lot of oil out the crank breather. Some have built small oil capture containers out of film canisters to help keep their planes cleaner.

Scott.