There is a reason that the OS91 is THE most popular ducted fan engine in use out there today-----ease of use and reliability.

Yes , the Rossi's can be real powerhouses--if you like to tinker and fiddle around all the time..........my opinion is that there isn't enough difference in the power output to bother with the headache of trying to get the Rossi to run --and the expense of putting an OS carb on? Guess I just don't like to fiddle as much as I used to.....OS for me..