Bigmon,
This project started out as a block of wood, then I cut the barrel channel and drilled\chiseled out the RR hole.
Then, fast forward to where I am now. Since every measurement goes off the barrel, I leave on a reasonable amount of wood and as I go through the process of inletting the lock plate and the side plate, I try to keep all 4 sides "square" to each other. Once I have the lock working, and the side plate inletted I then move to the trigger plate. Of course, I sand down the grip curve to where the center\middle will be but still keep the wood square. I also drill lock bolt holes and the barrel pin while I still have a square chunk of wood to work with. Today I'm removing wood from the RR channel to get it to a 1/8" depth. Then, while the wood is still square I'll inlet the RR pipes and drill the pin holes.
I guess what I'm saying is I try to leave the "block" as long as I can. That way I have something for the vice to grip and hold "straight and square". Once I have the RR pipes in and pinned I will inlet the TG....the start the "final" shaping. FWIW
And....PS: I don't think a pistol is any easier than a full stock rifle. Dimensions, inletting and attention to details is just as demanding as that of a rifle. At least that's been my experience.
And it's true that Bob Roller does not have anywhere near "feeble". I'm sure he's forgotten more about gun building than I'll ever know.....but what he contributes now is always valid and helpful.