RE: Combat Models F-16
First, the OS 75 is not an rpm oriented engine. This aircraft requires a small prop and lots of rpm.
The ideal engine for use on this plane is the YS45 - only way to accomodate the very goofy fuel system, and develop good power.
Possble alternate is the Jett 50 or 60LX and a revised fuel system. (the 60LX was first developed for this aircraft).
Anything else weights more and/or performs less, and you are absolutely limited to a 10" maximum prop diameter.
The CBM F-16 was a fun project in its day ----- but its day was 10-15 years ago.