Bro, if you are gonna rescape... I have the following suggestion:
1) Choose the largest pieces for the base
2) Don't just lay the LR flat on the sand bed, play with it, rotate it around... you can also use 2 to 3 pieces to form a steady base (not necessarily stacking one on top of each other).
3) I would strongly suggest you use Epoxy to hold them together. Even apply a bit at the base (glass) to avoid the LR from sliding. If you have not put in the sand, I would suggest you add a piece of egg crate.
4) Create as much cave as possible. Caves must be hollow through the back (meaning not just a dead space to trap detritus). The hollow caves must allow water to flow from the front, go out from the back or vice-versa. Remember, any dead space is DEAD SPACE
5) Be patient, don't rush. It's not easy to achieve a good balance in scaping... but it is a very crucial step as too many of us (including my Percula 90) will end up unhappy with our scaping (due to lack of planning and knowledge) and there's nothing we can do... that's why the constant upgrading (one of the main reasons).
Have fun bro... it's not gonna be hard for your tank size... just gotto be patient