If you put your files in a directory, use IMGFILE=none and CHROOT=/your_directory in the .chroot file, and it should work. But this isn't the best way to do it; if something crashes in the chroot, you can't clean up very well (because you can't tell the system just to kill everything in a certain mounted partition, since that partition is the main system partition), and also, it seems to be a bit slower. I know, slower is weird. But true. Oh, and of course, you can only use a directory in a Linux file system, since you need file permissions to work. And not in your home directory.

You could repartition your SD card on a Linux desktop computer using gparted. Or, you can do the repartitioning on-tablet using PenguinBait's GParted for the tablets.