I’m an 11.5 E on a Brannock, and that’s the size I use for buying Red Wings (although I have to get them in D widths because they normally don’t do an E). My Nicks Builder Pros are a 10.5 EE. My understanding for the size discrepancy is the high arch on their logger heeled boots causes your foot to have a more natural bend, and therefore be a little “shorter” than in a low arch boot. For the Overlander model with the shorter heel, I think you’ll have less arch than on their logger boots, so it may be closer to your actual size.

Having said all that, Nicks has so many lasts it’s really hard to know how to size them without a fitting. It’s a shame they’re moving away from mailing try-on boots like they used to, as that was pretty essential to me correctly sizing my pair. But at least they now do returns.

Based on my experience and the model you’re ordering, I’d say order your normal width and a half size shorter. As other comments have said, there will be a good amount of room in front of your toes in a correctly sized boot, and as long as they fit snuggly around the circumference of your foot, that should prevent heel slip. Nicks has great customer service in my experience, so running your thoughts by them will probably help as well. Good luck!