Apparently Cessna engineers weren't aware of all the above problems when they designed the 337 Tractor/Pusher config you describe... You might check out KMP's model of the 337 [link=http://www.kmp.ca/product_info.php?cPath=22&products_id=29&osCsid=e9 b42ebc92bd13b3573e500322b99009]KMP[/link],, I talked to them at the West Coast IMAA flyin at Castle.. They seemed to think any too engines within the specified range would work just fine... No big deal... I think there are a couple threads on here about the plane and engines also... Been awhile though...