So, I went to my eye Dr. appt. He was a young Dr. in his late 20's, plastic surgery was his specialty.
He wondered aloud as to why they sent me to him and not Dr. Marvin. My alert went up also.
They had me do a field vision test where I press a button every time I see a light flash in a box. Checked the pressure on my lenses and looked at the nevers in my eye. He said all was good. I asked him bout my right eye and he said it looked like sagging skin hanging down and said he could fix that with a little nip-tuck.
I told him I had done the ice cube test the night before and my lid corrected it's self (which it remarkable did, my wife was impressed). He said that was not a very good test at all and if I had ptosis normally the lid is draped over the entire eyeball. He then proceeded to lift the drooping skin and said "We can certainly correct that by cutting" I stopped him there and told him I was fine with the way I looked.
Needless to say, I think I went to the wrong Dr.

Is the ice cube test a legitimate test for ptosis or will it work on anybody to help tighten the skin on the eye?

I can compare one eye to the other and the left seems to have enough muscle tone to keep the skin taunt vs the other eye is loosing the gravity battle.