Wait a minute, your gun prints 175s great and you are worried about 160s? Tell that outfitter to go jump in a lake, if you are shooting 175s great then partner you are SET for elk!!! Realistically a 7mag with stoutly loaded 175s is a good a long range setup for big game as there is going. Inside of 400yds there isn't more than a couple inches MAX difference between the 175 vs the 160. And the heavier bullet will retain the velocity and energy which yields penetration (the KEY too elk) all other things being equal.

Good luck and don't look back!
RA