Try sanding down to 320grit first, than polish it to 600 grit. Try 1200 polish if that is still early.
Tom Tomaras prepared this surface for one of my students' Ultimate Inferno(5X4).
When fine tuning, if I want to polish a dull oil ball, I always sand it down to lower grit first. Otherwise, you "relatively" sacrifice the midlane and make it too weak for the condition it is intended for. In other words, best way to fine tune the reaction while staying in more or less the same range in terms of oil handling capability, first sand it down, than polish it.
I have successfully experienced this on many Ultimates, Full Trottles, Killer Instinct Sandeds, Trottles, Phenoms..
Hope this helps,
Burak