If you have good consistent broadhead flight, you will be fine. I killed a lot of elk with a 390-grain arrow before I "knew better", including several pass throughs and a frontal shot that was poking out the hindquarter. Good arrow flight is your number one priority. Focus on that, a structurally strong arrow, and a strong sharp broadhead delivered accurately, and you will be fine. Elk are pretty easy to kill if you shoot them in the lungs/heart. If you miss the vitals, it's a crap shoot, and you may never see that elk again.