To mark the excess grip material that is above the grip frame edges,,
Place the grips on the gun and tighten.
Then with a very sharp and thin bladed knife,,mark the grip material by dragging the point of the knife along grip right where it meets the frame.
An Exacto-Knife is good for this or anything close to it.
You want to tilt the knife blade so that it marks the grip material with a scribed line and not make any mark on the blued steel of course.
It doesn't take much pressure to make the scribed line into the wood (or ivory).
Then remove the grip panels and take a soft pencil (the ever popular #2) and scribble over that scribed line,,then wipe of erasure it off.
That'll leave the scribed line a darkened line on this type of wood and easy to see when working.
Take one panel and put it in a vise so the area you are working on is comfortably above the vise jaws.
Protect the grip with padding of course.
Now take the excess grip material away. That from outside that scribed line and down to the scribbed line.
But DO NOT remove the scribed line itself,,at least not yet.
That will be the very last in fitting depending on how close you choose to go.
When removing this material, work from the inside of the grip panel towards the outside of the finished surface.
Don't try and do any shaping to the outside like blending the cuts in just yet.
At this point just file away that excess so it ends up being a flat edge itself that is 90* to the flat inside surface of the panel.
Don't taper it towards the center of the outside of the panel, you may take too much off and end up with a low spot when it comes to final shaping. Straight out from the scribed line.
Working from the inside of the panel towards the outside will help avoid splintering the edges as well when filing away matr'l.
When you think you have all the areas taken down to the line, place one of the panels back on and check the fit of the area to the grip frame.
You will likely need some more matr'l taken off here and there to get that perfect wood to metal fit.
Now the tedious work of that last final fitting. You can get as close as you feel you want to doing this. Just remember that if you take the wood below the grip frame at any point,,thats where it will be on the final product.
When satisfied with the best fit possible, of both panels,,place them both back on the gun and put the gun in the vise. Now shape the outside of the grips in the area where the work was done.
File those areas back to conform with the orig wanted shape of that style and sand it smooth.
Careful when working around the metal work and the last bit of sanding at the edges can be done with the grips off of the frame.
Fine NEW grit paper backed with a file or hardwood can be used here to just barely touch up those delicate edges and protect them from getting rolled over by sanding heavily and w/o any backing.
The orig idea of trimming down the wood to the scribed line but leaving the line still visible was to allow for the very last delicate fitting & sanding and not end up with the grip being lower/smaller than the frame.