I have an original that I have copied a couple times now, and it has a cast off with the over the comb tang. When I copy the rifle, I leave the line straight down the barrel center, down the tang until I get to the top corner of the front of the comb, and then I draw a reference line from the front of the comb back to the butt with the cast off I want. I bend the final of the tang to line up with the reference line and inlet it accordingly. Seems to work out OK. I leave the trigger plate centered like the front portion of the tang, and bend the rear final of the triggerguard to line up with my reference line with the cast off I have drawn on the bottom of the stock from the toe to the back of the trigger plate. Good luck with your build. I am slow and it takes me a long time to do the inlet without any gaps, but it is well worth the effort. I have another set of parts in the shop now that I plan on building like this.
Roger Sells