Ive not tried RS grips... but i did buy these :
http://www.wgcshop.com/wgc2008/main/...Y-ACC-RFGP03BK
and they had cut outs for the weights except the weights didn't fit so i dremeled and sanded and smoothed and eventually got them to fit.. the weights arnt super well fitting but they fit enough to not be noticeable when fully assembled.
I have also attempted to dremel out a full cut on a set of wood grips i made myself... this was exceptionally difficult and i never managed to do it.. I suppose it would have been easier if i didn't mind having very thick grips but i like a thin grip which is where the problem arises.
The thickness of the TM plastic grip that covers the metal insert is suuuuper thin, and even on the set of ready fighters (linked above) i ended up punching 2 small holes thru to the front.
Maybe your better with the tools, but it is very difficult in my opinion