I suggest the OP also check their technique. Such a minimal change in grip size shouldn't cause that much of a wrist issue.
In TomT's case, the grip change was, I'm sure, more dramatic. However, Something as small as adding an overgrip or changing 1/8 of grip size shouldn't be any problem at all. Consult with your coach, definitely. Or ask some pro.
Wooo lefties. BLX PS 6.1 95, customized. 345g, ~370 SW, 3.2 pts. HL