Last week I got around to working on the back. I started finishing the perimeter the usual way, with files and sanding sticks. Then I thought "I've got a perfectly good belt and disk sander in the garage, why don't I use that?" And I did.
Using the disk part of the sander, I carefully cleaned up the perimeter. I was able to do almost all of it, except for the "C" bouts of course. This morning I did those with a small sanding drum chucked into the large drill press. Not only was it hugely faster than doing everything by hand, the finish is much smoother and the curves are more consistent.
The only part that needed some hand-work was on either side of the tongue. That only took a few minutes with a sanding stick.