Another place you might check is Hogue Handgun grips. There is a guy there who checkers over the pebbled surface on 'take off' factory Sig grip panels.
Ken Werner (?) I think, is his name...dunno for sure.
There is no measurable reduction in grip circumference with the checkered factory plastic panels, but the subjective difference is kinda nice. Maybe its the difference between pebbled and checkered. I don't know, but there is a noticable felt difference.
Since you are gonna buy factory plastic panels, it might be worth it to you to try the checkered 'take off' panels from Hogue.
I like mine on the 228.
salty