20 gallon tank for a baby grey rat snake?

[CosmicOwl]

I recently acquired a baby grey rat snake and have been keeping him in a small sterilite tub, secured with binder clips. However, I've read from a few different sources that they are quite active and enjoy climbing. I know the general rule is to keep baby snakes in small enclosures to keep them from getting stressed out, but this little guy seems to be adjusting to his enclosure well. Rather than staying hidden away, he spends a lot of time roaming around. Provided he has plenty of hides, do you think it would be beneficial to put him in the 20 gallon tank? Or should I just keep him where he is until he puts on some size?