No bands.
Very strict. My son was measured outside of Star Tours and was told "OK". Then when he and DH got to the very last turnstyles well inside the line, when you're sent to your star freighter or wherever, the CM measured him again. Slid a piece of paper between the post thing and DS's head, the paper went through, he was booted.
However, he did get a cute card with Stitch on it saying that Stitch understands what it's like being small, but when he's big enough to come back and he and his family can ride.
We took it to Star Tours on this trip (b/c we forgot to last trip) and were sent straight to the front of the line, after they wrote the date on it and gave the card back to me. Nice moment, and nice scrapbook item!
DS got measured for Grizzly twice this time (he wouldn't believe us that he wasn't 42") so now he has two of those cards for Grizzly, though it's not Stitch on the card.
Practice with your son to stand up tall, and to NOT let anyone put anything above his head (my son was truly tall enough but he slouched down when the guy was trying to put something on his head...he was only 3, he was trying to be nice and compliant with employees of
Disneyland, ya know?).
Being big for Star Tours (and know being big for Grizzly) was a great way to get him to eat proper food. I'd shy away from the cow's milk though, it actually robs your body of calcium and makes it harder to grow bones (digesting the protein takes more calcium from your body than it's fortified with, so we end up at a negative CA amount when we eat dairy). We focused on whole foods, veggies, that sort of thing.
Based on our experience at Star Tours, and knowing that not all the measuring sticks are necessarily exact, but at the same time they are Disneyland LAW (you can't argue with it, they don't care), never EVER tell a child that they WILL ride something, not even if you're in the line. OK, once they are 42 inches you can tell them they can ride a 40" ride, but until then, it's not a good idea. Always talk about "let's see if we can ride this this time". Otherwise you're just setting up a child for disappointment when the measuring stick is weird, when they are slouching, when they get a paper-wielding CM, etc etc etc. Or if they went on BTMRR 4 times that morning, they'll squish their spines down a bit, and they might not BE 40" by the time you want to go on star Tours that afternoon!