Richard: Why cut off rotary rpms at 7500 ? 8300 at 3.3:1 would make a nice 2500 prop rpm package and 9000 would give you more range than any old lycoming.  And, the idea of two 38 mm mikunis sure sounds like a nice way to eliminate a lot of problems. How much does the hirth g40 weigh ? Wonder how much more than 140 it would take ?

jofarr, soddy tn