thanks. very simply, i used some masking tape to protect the top side of the insert and i used, very sparingly, a light sanding disc on the dremel and bit by bit, slowly sanded down the underside of the insert, stoping after every few pases to check the fit.
it definatly took some time, and i practiced first on 2 mbw insertsm which are exceptionally weaker then a gen insert, which was suprisingly strong, even after being thinned out. it was a pretty simple job, just requires some patience and presicion, like any other mod.