Thanks for the link to Delrin Shims made to fit between various model RDS and mount. Good to know I'm not the first to run out of adjustment; and no need to reinvent the wheel. 
I just ordered a set to try. They're cheap enough, I wish JPoint had supplied them in the first place.
be careful when tightening or loosening the adjustments , I cranked my elevation down all the way and killed my first one.
it took almost a month to gt a new one sent back from England. over tightening any of the adjustments will short the light circuit and you're
out an RMR. I would call Shield and ask them to send you a couple, they will send them (we're not the first to complain about this)
but it will take a while for them to get here. the Delrins shipped almost overnight and on my M&P < had to use both
the one shield sent and the Delrin. the one shield sent my was quite a bit thicker than the Delrin too.