I've only climbed a few sticks up with my new one sticks. I wear a 12 wide in most boots.
No issues. Just duck foot it or put the foot half on, lean back into the lineman's, and plenty of room. I'm not on the stick very long.
I climb with the tether attached also, so if I was ever on a stick for too long, I can always make the tether extra tight and sit into the saddle.
Seems like climbing on a tether lends to a more vertical orientation than climbing with a linesman's belt. That's probably a good thing, as it weights the stick in the direction of intended stress.
Do you do anything special to manage tether slack while climbing?