I am new here. Why would you cut them down?
If you fit 11 frames in a 10 frame brood box, or 9 frames in a 8 frame brood box...Your in essence gaming the system, that extra frame allows for more comb, hence more cells, hence more place for the queen to lay, hence more bees in the same amount of space.
Sort of the opposite of what a lot of folks do in their honey supers...One less frame there allows for thicker comb. The folks that do it claim you get more honey, or at least as much, per box, with the thicker comb. Advantages are fewer frames to uncap and extract, as well as being easier to uncap.
Not saying I'll never give one or the other, or both a try....but for now, I'm content simply using the standard # of frames in both my brood boxes and honey supers.