If you are going DSB, be aware that the eggcrate is very damaging to the functionality of a DSB. If you want to go that route AND protect the bottom, starboard (aka cutting board) under your sand might be a better option. If it's just a layer of sand for aesthetics, the eggcrate will reduce any critter population but that's not critical for a shallow sand bed.
(But I like having a live shallow sand bed; the critters clean up the sand for me.)
To prevent rock slides, you can always chose to drill your rocks and secure them with acrylic rods or other methods.