It seems that I just cannot help but post things prematurely! I am trying to design a different kind of sled. This is my first mockup. It has some interesting features (which may or may not be useful).
1. If the board is mounted 1/4" proud of the top, (as in the second picture) the machine measures just the board.
2. The board does not need to be clamped, taped, or screwed onto the jig. It just sits there.
3. The board can be removed from the jig without lifting the head off of the jig. I am hoping to use this feature for accurate double sided carving. It can also be used for mass production. Pieces can be swapped in and out without the machine having to remeasure. (This, I think, will require the sandpaper rails be flipped over. The board can slide out the front.)
4. Cutouts will not cut into the jig if they stay 3/4" away from the sides. (I assume larger tabs will be required but if a piece does fall out, at least it will not fall between the belts.)
5. Except for the need to use Jog to Touch, jig operation (for carving and cutting bits) can be the same as if the board was down on the belts.
My main motive is to develop a better method for double sided projects.