I know radiation side effects come in different forms at different times. The lymph node area in my neck that was radiated has gotten more stiff over time and tightens up and will have a spasm now and then. I bend and stretch my neck many times during the day and that helps alot.

Not sure about migraines as that is something I've not had. As far as helping with mouth opening issues, why not just try popsicle sticks. It seems so much more practical and easier to use. Just add a few to get the right thickness, add another as you can tolerate. Cut and tape together to make a nice compact device.

Good luck