Shot placement is the biggest key. Optimally, hold out for a broadside shot and double-lung him.
Personnally, I will only shoot four-blade broadheads (I lost an elk with a two-bladed broadhead that was a perfect broadside hit).
Also, if your bow will allow you to turn up the poundage above 50 , and you can still shoot it O.K. , do it.
Above all practice judging the distances. If you are wrong by only a little the result is a bad hit or a miss.
Generally, a heavier arrow will penetrate better, but if you get the broadside shot you should be fine, just get those four blades cutting through BOTH lungs, or you will be tracking a very long time.