I have never personally met anyone that has lost an elk due to low poundage. I think sometimes poor penetration gets blamed on low poundage when it fact they were shooting at extended ranges, put the arrow right on a bone or shoulder blade, or poor broadhead choice. Bottom line is, from guys that I know who have lost elk, they made a poor shot and/or did not wait long enough. I would not hesitate shooting low 50's for elk but my 25-30 yard shots would be out of the question. And 10-15 is what I would have to have.
We should not be debating poundage because ft/lbs of energy would be more informative. Who cares what the poundage is considering the major differences in efficiencies. Just one personal example. I have an 80# Bushmaster Hill style longbow that I think shoots very close to the same speed as my Centaur Chimera at 65# with the same arrow. Also as previously mentioned, you can't put too much stock into what is written on the bow.
Arrow placement will always e the most important element. Out of control increased power will do little to help you bag an elk.