2 cents from a running enthusiast here, I've done training runs, couple of 5Ks and 5 mile races on both 10.5 (a bit too long but was remedied by wearing double layer elite basketball socks which also helped when it was still very cold) and the replacement 10 and I had no problem with heel lockdown, right or left. There's a couple lacing techniques that you can try in case of poor fit. fwiw each set of feet are of course unique. That's what I like about RRS VIP, you can always try shoes out, return and exchange as needed.