1500 polished is the worst finish EVER for over under. Always change a 1500 polished ball to another surface. I abhor it.
The main problem is Storm's version (or definition, if you will) of "1500 grit polished" becomes, in practice "4000 grit + polish".
Near as I can tell, sanding a ball to 1500 grit and then applying a coat of polish makes for a great surface, in general, for many balls. "1500 grit + polish" usually results in the bottoms of the 'peaks and valleys' to be 1500 grit and the polish causes the peaks to be around 4500 - 5000 grit.
On the other hand, Storm's stock "1500 grit polished" causes both peaks and valleys to be in the 4000 - 5500 grit range.
This is sort of like the difference between sanding a ball with 500/1000/2000/4000 grit vs. sanding it with 500/4000 grit.