Steve you are to be commended on the detailed work you've accomplished here. I spend about an hour inletting a butt plate, after it is filed to 'ready' stage. But I do not go to the trouble you have...not even close.
I bandsaw the inside lines of the plate, and rough fit the return so the plate will roughly sit on the stock, oriented to the centre lines. then I draw a line around the outside of the plate, and with a big gouge and a heavy mallet, I remove wood to within 1/8" or so of that line. Inside the line by again about 3/16", I use a fish tailed gouge and remove the ground so that when I'm fitting, I do not have so much wood to deal with..only the edges. So the return is inlet down and forward until the vertical part comes into contact in the upper corner. Often, wood has to be removed from the toe area so that the whole plate will move forward enough to contact in the corner of the return. When the return is down and parallel to the top of the comb, and the butt plate is in contact for about a third of the way down from the corner, and the toe is in contact for about a third of the plates height, the rest of the plate will be very close to fitting. I install the screws, and with a small ball peen hammer, I tap the rest of the plate onto the wood...gently. The brass only has a few thousandths of an inch to go to make a perfect fit, but it saves hours of time, tapping it down, removing the black, tapping it down, removing the black, und so wieder. I think I stole this method from John Biven's collection of articles for "Rifle" magazine, in the last century.
But let me say, I admire your patience and stay with it attitude.
