Here's my 4Star60 with a Saito 91 mounted. The mount is a Hayes AL60. That same mount has been used to mount an OS 61 FX, OS91 FX, Super Tiger G90 and a YS110. The mount location is consistent with the thrust line. Yea, pulled the cowl cheeks off so that it would be easier to use the plane as an engine mule.

The only issue with the different engines has been the throttle control. Iuse 2-56 wire thru some sort of tube. No problems. In some cases the throttle carb arm needed to be rotated or the carb mounted in reverse of "as delivered" - swapping the high speed throttle from the left to right or right to left - what ever was needed to be able to safely access the tuning adjustments when the prop was turning.