The Fox .45 would not be heavy since the Fox .50 is the lightest of the .50 sized engines, weighing nearly an ounce less than the Webra .50. Both of my older Fox.50s and my Fox .46 turn a 10x6 at 14,400, the one I rebuilt recently turned a 10x6 at 14,140 with less than an hours time on it. It's now a Diesel. I have owned as high as 3 ST. .51s at the same time and they are stone reliable workhorses. One was roasted so bad by my son-in-law that the early bullet muffler separated at the joint and the engine was forever a dark gray color but soldiered on just the same.