I just had a call with the same scenerio. A guy had a Euro from 3 years ago...he is kicking himself for not shoulder mounting it. His buddy shot a similar aged buck with similar mass. I didn't charge extra as there wasn't any additional work to be done. I always keep about 3-4 extra capes in the freezer just incase someone needs to buy one.....if this is the case, then of course the mount will cost extra. Each taxidermist may be different, but I don't charge extra if there isn't any extra work that is needed. As far as size, it is easier to cut the antler burrs of a cape a little bigger to fit a rack than it is to go the opposite way (larger rack to smaller rack) Just try to find a nice looking cape, similar age, and similar mass to the buck your mounting and you won't have any problems.