As long as you can fit the string through the hole, you'll be OK. You want the B and E string holes to be as low as practically possible so you don't need to use string trees.
I fitted some of the Hipshots (enclosed versions) to a friend's Fret King, where the original height-adjustable Gotohs just weren't locking properly. I used the backing pieces and that covered up the holes without needing to do any filling-in.
Last edited by Simon Barden; 29-02-2020 at 05:39 PM.