So far I have worn them twice for many hours and they started to blister the back of my heel, my IRs, 8181s, Brogue Rangers, and postman oxfords have all done this until broken in. I wear 9.5D in all of the RWs I mentioned.
Next time I wear them I will try to determine if my heel is moving around more or less than my other RWs and let ya know. So far theyou do feel pretty stable, I can definitely tell the boot is taller and supports above my ankle more.
Looking forward to your update.
Regarding blisters, I have been experimenting with some socks guaranteed to prevent them...they seem good so far...they're two layers stitched together: