If the stock was hollowed out to that degree it was likely for balance. Lay out your cut for your comb without regard to the hollow. Cutting it too thin from top to bottom could likely make it uncomfortable to shoot. Glue blocks in the needed positions inside the stock body and the comb and then inlet your hardware. It is easier to inlet the round hardware. remember to check what adjustments are possible with the hardware. most only move in 2 axis. if you need to move the back of the comb up you have to drill the holes for the comb to achieve that angle. Hope this has been helpful.
