So is height as much of a concern for froglets? Every article I have read on the subject is pretty much for terrestrials. These are my first babies, and I raised them insitu but they are coming out fat!! I think I will have to move them soon. Those front legs can't hide for long!
No, it will be fine for thumbnails. Thumbnails are my passion. We use this kind of container all the time for froglets all the time while growing them out or waiting for the time to build the next viv. Make sure you supply leaf litter for them to hide in. A piece of live Pothos will be appreciated. They would probably use a piece of wood too, but that's not a deal breaker. If you have a piece of ghost wood that is going to go in their viv, why not store it in their grow out container though?
People have even used plastic shoe boxes to grow them out for a month or three.
This is the thread I read for temporary containers. I bought a bunch and love them. I did use one as a temporary container for 8 month old tarapoto thumbs and it worked very well. They were in there for a couple of months and they were already courting and such. The only problem is you can't see through it easily. Only problem is Target doesn't sell them anymore as far as I know. You might need to find them online.
I have recently gone with going to the $1 per gallon sale at Petco and getting 10 gallons as temp containers. I use them horizontal and the frogs don't mind one bit. They love them and I love them because I can see them clearly. So, $10 for the tank and $10 for the glass lid they sell and some tape(or use Saran wrap). Not bad, I think. Stick a piece a wood and lots of pothos and leaves and sphagnum moss.