Good arrow flight, very sharp two bladed broadhead and you will be golden.
One of the nicest fellows I have ever met was a fellow who one the recurve division at one of the first Denton Hill shoots, he was in his late 70's, his son won the longbow and his grandson was shooting with them.
he sat down with me at my Renaissance Archery booth and talked awhile. He shot a 43 lb. bear recurve. Hunted everything with it and had been doing so for thirty years.
Deer, bear and I believe some big game hunts with it also.
Same bow, same arrows and broadheads.
I would have no doubt about your fathers hunting with a 40 pounder.