OK, so the box is 4.5 x .5 it represents the plank of rose wood i am using.
and the semi circle inside is a 9.5 in radius circle. same radius as my fret board
as you see the radius force the wood to be about 4-4.25 inches wide when the width is .5 inches. unfortunately the space under the strings is much less than that so the ramp will probably end up being less and 4 inches wide. which isn't enough to reach the outside pickup screws on the p pick up.
it seems i will have to keep the pick up covers on after all.
i think i will route my neck cavity and pick up holes into the wood first then radius it and see what happens.
FWIW if the radiused playing ramp doesn't work out for me then I'm willing to try a flat "playing shelf".... it don't look half bad