Hollowing the Back Plate

Now that the arching of the back plate has been finalized, the next step is to hollow the underside of the plate.  In my case, because my arching ended up a bit low, the plate will be graduated in thickness from approximately 5.0mm in the center to 2.8mm at the top and 3.0mm at the bottom.  To mark the graduating zones, a plastic template is traced onto the underside of the back plate:

Holes are then drilled along the traced lines of the appropriate depth using a drill press with a micrometer to measure depth of the hole.  This system is designed so that wood can be removed until the drill holes disappear, and at that point, the graduated thicknesses will be correct.  Here is the marked and drilled underside of the back plate:

Then the wood removal begins, using a chisel, thumb planes, and ultimately scrapers:

Here is the hollowed underside of the back plate: