Mike, just install the Hardpoints footers on top of Relaxa platform.
I could try that, but combining passive anti-vibration devices typically is not the recipe for success, unless engineered to work that way, or in one device.
I have limited sets of the Hardpoints. right now I use 4 sets of 4 Trinia's (under the 3 MSB boxes, and the Tripoint Elite) and one set of 4 Serene's (Tripoint Troy Sig). if I pull one set out then my overall sonic picture changes. and in my sonic food chain the Poseidon is down the list from those other uses. it's likely next worthy (considering also my Taiko (SGM) and Herzan (dart pre & NVS) units deployed).
so far after a day, i'd say that the 'overweight' Relaxa 1 under the Poseidon is close, if not quite up to the level, of the Wave Kinetics A10 U8's it replaced. would the latest Relaxa 530 sound significantly better? you would expect it to be some better.
I have 8 sets of A10 U8's in my system, and there is a good reason that the Relaxa 1 was previously sidelined. I try it from time to time in places, when I run short of A10 U8's, but the A10 U8's seem to do a better overall job. I have also compared the A10 U8's now to the Hardpoints in a number of places and that is a very significant consistent delta favoring the Hardpoints. a couple of levels better.
if/when I do acquire more Hardpoints I will try them under the Poseidon. that is probable. their floating/decoupling ability is quite amazing. and they bring an expressiveness, focus and nuance aspect to the music as well as tonal deepening, without any hardness or sterility.