If the ASP 1.08 is the same as the older Magnum 1.08, it tends to be a tractor engine, rather than a sports car engine. We have found a 15-8 or a 16-6 is the best prop. The smaller and lower pitch props didn't turn that much faster to make up the difference.

On a sport plane, I run a 16-6. On a scale plane that I want a little faster, I run a 15-8.