Summary

Modified this to better fit my tablet, maybe others will find this useful. I used a 10-24 threaded rod to connect the top and bottom clamps.

I also added some flex seal tape so there is some rubber cushion on each clamp slot, you could use any soft / rubbery tape to add a non slip grip.

The knob at the top has an opening for a nut for the 10-24 rod, I heated the nut just enough to press fit into the plastic and it keeps it secure, but if you wanted to glue it in, that would work also.