You're totally right. I've had various checks work and then fail. And I know what you mean about your hands being so clear. If the dream looks and feels that incredibly real, reality checks might not work, for the reason you mentioned about your brain having a firm grasp of physics.

I don't have a 100% perfect solution, only something that has worked for me over and over, and that's looking into a mirror. It hasn't failed me yet, so maybe it's just a matter of sorting through different RC techniques and finding out what works best for you. But I agree with you, none of them are certain. My mirror might fail me one day, but I dare it to try!!