I know this might offend some guys...but if I lived out west, and planned on hunting elk on a regular basis I'd work a bit on getting my bow weight up to the 60lb range if possible and plan on matching my arrows at 600-650 grains (as opposed to your 50ish/500ish grain arrow). Elk are tough critters, amazingly so sometimes, and a little mistake can get big fast. I know so-and-so shot an elk with a 40 lb bow one time....great, and I've got a buddy that is a crazy-serious elk guy that spends a month every year living in the back country hunting them and has shot a bunch of bulls with HH type bows in the 70ish lb range, and typical cedar arrows probably around 550 gr. He has plenty of stories about marginal penetration on decent hits, with this heavy equipment. Everyone assumes "hit them where you should"...well if that was a given you could use any equipment and be fine. I'd caution folks that plan on hunting elk seriously, and often, to treat them like exactly what they are...a 500-800 lb deer....and if you think a 250 lb mature whitetail is tough (which they ARE) imagine him being 2-3X bigger.
Of course some folks can't or don't want to step up on arrow/bow wt, and have to figure out something that will work for them....but I think it is a dangerous slope to always talk about "whats the minimum bow or arrow weight to hunt X animal".....
My elk killing is limited to 2 bulls, one "average" body size and one "great big" body size, but when comparing them to other large bodied animals I've killed in the US (moose, musk ox) I think elk are significantly tougher than either of these 2. For what its worth these bulls were both killed with 60-65lb recurves, aluminum arrows in the 625-650 gr range, and both were complete penetration with big Snuffers through the chest. The big bodied bull was hit through both lungs and large arteries over the heart, center chest, and went every bit of 200 yards flat out. Plenty of blood, of course, but I was surprised he went that far hit that way - a testimonial to a rutted-up mature bull elk's will to live. Total shot distance on both bulls added together was 12 yards (one at 5yds, one at 7yds).
R