RE: Montana Elk Decoy on Rifle Hunt?
I'd say buy the full side decoy, give it to your friend as a gift, (unoppened), and leave the cow calling to the more experienced. All you will do is educate the elk as to where you are, and will avoid you like the plague.
Elk hunting with rifle is more about scouting, patterning, climbing up & down mountains, and hunting your quarry. It's not the rut, and the elk will likely not come in to a cow call.