I wouldn't go for MDF and I think microjig recommend to not use MDF?
Other than that, using the dovetail clamps (or regular rail clamps in routed t-slots) is in my opinion superior to other hold down methods in most cases. Quick to slide to new position, easy to change height, quick to move from jig to jig, easy to control the pressure, can be used in thin jigs since the force is taken up in the clamp itself, whereas a toggle clamp is pretty much the opposite to all of the above.
I use rail clamps (dovetail clamps where not invented by the time I started using this concept) in almost all my jigs since a few years back. I haven't had problem with the plywood bending but I might have been lucky. I would point out though that it's very seldom I rout the tracks from side to side going through the entire width/length when it comes to thin jigs. I often keep one side full thickness, without tracks, for rigidity. In your taper jig, if you slide in the clamps from the same side as the workpiece is, you could have full thickness plywood without cuts on a large part of the surface, left of the clamps in your pic.
My table saw sled was my first "rail clamp in jig" build some 8 years ago, the routed tracks have survived well and it's really great! I can clamp any item of any size almost anywhere I want and it's done in seconds. I can also clamp additional jigs to the sled, like in sample pic attached where I cut drawer pulls to length using both a stop and a jig to hold the pull, both jig and stop attached easily with rail clamps.
See pinterest or yotube link for more examples where I use rail clamps in jigs.
Last edited by Ola C; 12-04-2019 at 08:26 AM.