Shane,
Cedar is a pretty wood to look at .....but IMHO for tip overlays it is too soft of wood. Overlays are to protect the bows back from splitting from the string. Antler , horn or a harder wood would be a better choice. I have some scrap osage pieces you can have if you like....osage gets darker with time and would be a nice looking contrast to hickory....just offering.
You should remove that first layer to add the overlays. That pignut hickory back is a little different than other hickory I've cut. I don't believe it is the cambium layer you seeing. The bows I've made out of the same tree I lightly sanded the back to remove the dark colored ridges. I don't think you have too though.....except under the overlays.
Look'n good so far, that is some exceptional hickory if the RH is low you will be surprise how thin the limbs will be for the weigth....
Good luck and keep us posted..
DBar
Oh let me know on the osage material and I might have some other woods too if your interested.