I'm not trying to downplay the need for KE, but here is some food for thought. When mechanicals were in their infancy I used Punchcutters which had a notoriously inefficient design by today's standards. I shot them off of 27" 2213 XX75s at 423 grains going a whopping 217 fps for a total KE of 44 ft. lbs. I took a number of deer with those and the only one that failed to produce a pass through hit the far shoulder blade and still punched through partially.

With today's broadhead designs combined with the efficiency of modern bows there is little to worry about. I think he would be fine with the Rages.

On the other hand, if you have the Montecs flying well, why chance it. You already have a set up that works, so go with that.