One lesson I learned by learning how to setup my tank:
Don't agonize too much, just take your best shot because in a few weeks you'll probably be moving it all around! To my eye, the big rock looked better on the side IF it is to be balanced with a bunch of plants. Also:
- don't forget that you will probably want some tall bg plants, so leave some space back there!
- mind your flow- those little crevices can become messy!
"The fewer our wants, the nearer we resemble the gods." — Socrates