We just doubled up on the struts after putting an 18" deep memory foam mattress on the bed. The original struts were already pretty much done. I picked up a pair of 90lb (I think) struts and the weight of the mattress kept it down. Lifting was easy peasy and the 4 struts kept the mattress up in the air until pressure was added to bring it back down. Some trial and error was required and, of course, YMMV.
Cheers!
Mike