Folks,
Thanks for your comments. As you have recognized, my approach--which is tailored to bee boxes--has some unique advantages:
1). Safety -- there is little opportunity for operator error because the blade is completely shielded and dust is minimal with a good vacuum system on your saw. (Instead of my approach, if you would use only the saw fence with the 3/4" dado on the outside of the board you would have exposed dado blade and a cloud of dust right in your face).
2) Efficiency -- I can lift my box joint jig off my table saw, mount the frame rest jig, and start cutting frame rests without changing the height of the dado blade or anything on the saw. (Note that the math works out as long as the base of the frame rest jig is close to the thickness of your hive boards).
3) Adaptability -- the jig is completely independent of the size of box panel (deeps, mediums, or shallow) into which you are cutting the frame rest. To match this by doing it only with a fence you would have to have a board mounted vertically along the fence to offset the box panels from the fence
4) Cheap -- you can build this from scrap laying around your shop.
So even though table saw sleds have been used for a long time, as far as I know, this is the first time one is used to cut frame rests.
Carl Korschgen