The Ramtec fan does not work well in airframes with small inlets. It has fewer blades, but more pitch. The engine turns fewer RPMs than it would in a Dynamax.

The Dynamax (IMHO) is well suited for any airframe. I have flown a Dynamax powered Starfire at 200MPH. I have also seen a friend's Dynamax powered 30# JMP T-33, fly very well.