Yep... 9 3/4 would give over an inch spare to either side. JW is closer on his measurement.
i tried nuc;s with a 1 inch hole, but I really missed being able to stuff a feeder in the front. I also liked being able to reduce the entrances, or open them up if I stacked another box or two on top of the nuc..
A lot of folks say the boardman feeders induce robbing, but I have found that when they are used with a reducer, forcing entrance on the opposite side of the feeder that robbing has not been an issue... though I try not to use them during times of dearth or in the fall. I normally open feed well away from the hives, but a nuc struggling to get going seems to benefit from their own private supply.
I have considered plywood for the sides and may one day give it a try, but usually the only ply I have is 1/2 inch and that seems a bit thin to me. if I manage to procure some 3/4 I may try it and see how they hold up.
Went to a beekeepers meeting tonight, and afterwords directed the wife to the infamous WalMart, and returned home with a new camera.. If I can ever figure out how to make it take a picture I will be able to add visual stimulation with colorful mind enhancing pictures to my seemingly unending dialog... MUAHAHAHA