Oh my gosh, isn't that so frustrating! He's a BIG cat, so I can imagine how much of an ordeal it is if he doesn't want to cooperate!
Have you ever tried the clothespin trick? I haven't tried it, but it seems like it works well for some people. Many people use the burrito method, but Tinkles won't tolerate that type of restraint. I actually had my hubby or daughter just pick Tinkles up and hold him in the beginning when he was ornery about taking meds or getting tested. Can you have someone help you until you get him into a good routine?
My hubby can't test at all, Tinkles squirms and runs away...and hubby lets him go. Since he gets away with it, he knows he doesn't HAVE to hold still for DH. I never let him get away with that, so he knows he HAS to let me get the test.
Sometimes it's just a matter of finding out what works best for you and your cat. Once you find the system that works for you, it will get easier. Good luck, look at the home testing links, maybe an idea there will help you out.