I can say for white tail I wouldn't be concerned very much, I use a weight of 520 grains on elk( almost all shots are within 15-17 yards). I have seen upwards of around 30 bulls killed with the bow, and have seen some bad results with lighter setups. Situations where the arrow ricocheted off the ribs and ended up angling back on a broadside shot. These bulls did die, but the blood trails were long.

80 lbs of KE with a 520 grain arrow is not the same as 80 lbs of KE with a lighter arrow. I don't know if bowsite.com still has the study that was done when coming up with a cape buffalo setup. But all tests showed that the hunter opted for an 820 grain arrow hitting with the same ke as an arrow hitting with half the weight and the same KE. Momentum is usually overlooked and is a great factor to good penetration. The lighter arrow even with the same KE, will give up the energy much quicker after the initial punch.

If your stuff is tried and true, then by all means use it. It will always be heavier for me.