I have been shooting a thumbhole stock on my Knight Disc Extreme, and on my TK2000 for several years now.
I now prefer them over a conventional grip; they are very comfortable for me. IMO a thumbhole can be held steadier in and off hand shooting situation.
I have never experienced any problems shooting them with while wearing gloves during the Late Muzzleloader Season.
Thumbhole stocks do take some getting used to initially. Practice some, and the thumb hole becomes an automatic.