You only need one (or 2 at the most) set of leaves above the sand & one set of leaf nodes is sufficient under the sand. Sounds like you could get a few more cuttings from your 10 inch cuttings.
Ellie

Forgot to ask-- did you cut a hole in the bottom of the small container so the sand stays REALLY wet- the water below isn't just for humidity- it's to keep the sand wet at all times. You're growing your cutting in the water- the sand is just to keep it standing up straight- which it will do if it's shorter. If you didn't cut a hole it won't be wet enough & the cuttings will wilt.

I did put holes in. I figured the sand had to be sopping wet. Then I can water from below too to keep it wet. I did think of cutting up the long stems and making more sections, but I donÂt know what IÂm going to do with these as it is! I have a lot of tubers started. They were too leggy and I knew I had to cut them down, and hated to waste anything.