Greg, you have it right.
I have a Diamond Pro. In original configuration the corners were 4.5" and the sides were 4.875", in effect, Pro Cut. Although at the extreme end of "enjoyment and challenge", the corner pockets were playable. BUT, at 4.875" the side pockets were not. At that dimension they literally changed the character of the game. The most basic shots were reduced to such low percentage that play became tedious and literally beyond challenging.
Thus, when I re-configured to 4.625" and 5.125" the table is at least playable but as I mentioned, and Greg has observed, it is still very demanding.
Diamond was the table vendor for a seniors event held here in Naples FL about two years back. It featured a galaxy of top level players; the side pockets on those tables measured 5.125"; that's how I arrived at the present dimension.
Having gone through this whole odyssey, I am convinced that a super tough table does not necessarily produce better skills in the long run. The balance between frustration and confidence is subtle.