Always, always choose a fitting width first and only then the length. When you use a snug last, the size you take can be 0.5 sizes too long and it makes no difference on how the shoe fits. Shoes primarily fit because of a good last width and instep, not because of the length. Length is only a secondary or tertiary concern when choosing shoes.
If you have a Brannock measured US C width not borderlining B/C, I'm saying you can forget about the New Rey from this point on. It will not fit your feet. Choose the next width up and compensate with tongue pads, if necessary. If heel slippage will be your only problem in Olfe, Hiro or Ben lasts, you can fix it with tongue pads and insoles.
A forcefully stretched shoe will never fit perfectly. Don't even consider that.
Thanks for the advice. I'm closer to borderline C/D, so I think it's time to give something on the Hiro last a shot. The biggest issue is I've had some gapping on the sides of my heel with D width shoes. Heel slippage is not as much a problem. C width is almost too tight in the toes, and this is where it seems like the New Rey would be most constricting, so it's out.