It is difficult to see in the drawing but I put holes in the fences to allow me to use bungees to somewhat support the work. Left hand on the TS, and right hand holding the work should allow pretty quick, repeatable action. The table saw jigs I have seen mostly don't use clamps to hold down the work, obviously the inverted nature requires something to hold it up...
Being an exreme novice, but pondering this quandry, it seems that a router with a straight cutting bit could be used to achieve this joint
Clamp the corresponding pieces back to back (mitered edges forming a 90 degree point) and use the router to cut both pieces at the same time, ensuring perfect allignment.