Wah... 4 ft acrylic......
yeah was thinking about the rocks falling too.
Would like to have a lot of caves and crevices so that fishes can hide.
I do not think I can find a big rock with those.
Most likely will get several small pieces with nice arcs, glue them together and have 2-3 separate large rocks.
I will not glue all the rocks together incase if i need redo some aquascaping for corals additions.
But yup, thanks for the advise on rocks topping.