RE: fastest prop
To go faster you need MORE pitch and MORE rpm. More diameter hurts you both ways. A mousse can pipe will add 1300 rpm to the OS 40.The SPADTOTHEBONE web site has a great how to article on MCPs. On that plane you could try an APC 8-8. If the plane launches real well with the 8" prop, try a 7-8 prop. The carb on the LA40 is restrictive, and my LA.40 responded to opening it up a drill size. I also have the C/L venturis, but haven't gotten around to using one for RC yet.