yeah. eggcrate woudl be a useable option. i have a bit on the bottom of my 40 breeder holding up my ORA duncan. with an 80X turnover rate, the sand can get kinda disturbed soemtimes, so i have it there for security and it works well.
but in a 90 gallon tank, i would start the coral in the middle of the tank and work yoru way up.