ya, hard to plant well in a 10g. i just bought my 2nd Vivarium last week (comes in sometime in the next couple weeks).
had originally set forth for a 10g-hex but just couldn't imagine how to plant it, so upgraded to a 17g-hex. will still be tough, but even a few inches helps.
good luck with it!
if you need pointers on how to plant it well and have runnign water, etc, let me know. otherwise, check out DendroBoard forum. It is a Dart Frog forum, but many specialize in Vivarium construction.
www.dendroboard.com