I then mounted the grip frame, making sure that it was perpendicular to the back edge. This is important, as the front will be propped up later to level the fill line.
Placing my hand on the grip, I used a red magic marker to make an outline of my palm's profile. Taking some mesurements, I was able to make an mirrored, symmetrical palm shelf. To come up with the curves, I simply used a penny dead front of the grip, and a nickle at every other corner.
I realized this morning that the symmetrical pattern wouldn't work for me, due to the folding stock I was installing below the palm shelf. I cut away the offending walls of the mold; mounted the stock in the folded position; referenced the position with the red marker; than made a new outline on that side, again using a nickle to round the corners.