Mate if i had your set up and a white tail popped up upto 50 yards infront of me I'd nail him. (Mind you I'm from Australia and we don't have whitetail over here) Providing he is pretty relaxed that is, as this decreases the chance of him jumpin the string.

I personally think it's up to the capabilities of the hunter. If you can get 2 inch groups at forty yds, thats more then accurate enough. Remember it's more about shot placment rather than distance I think.

Cheers,
Stalkin Steve