You mentioned the Philidelphia collar. It looks like it would give more support for sure. I am going to order one and give it a try. I know the soft collar has helped reduce some of my symptoms. Headaches not as often, not as much shoulder, neck and arm pain, hoarse voice or voice dysphonia is less frequent and less tinnitus has been reduced, numbness and tingling and pain in arms and hand as well is less there are others symptoms too but these are the main ones I will list. The tension and pain cycle felt like it had been kind of eased for a while and that without drugs I was so happy. I will let you know how the other one works.
PS, I notice that there are two different types of philidelphia collars have you tried the Philadelphia Patriot One-Piece Cervical? It looks like it might be cooler for summer?