Is there any need to protect QuietFloor Plus from heavy point loads?

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I am trying to improve airborne sound insulation through a timber floor in a first floor flat. The timber floor is constructed using plain (not T&G) boards, but cannot be taken up, because dry walls have been built on top of it and technically it does not belong to me. I am presently thinking of using Acoustic Foam to fill the 2 - 3mm gaps between the floor boards, one layer of SBM5 and one layer of 15mm QuietFloor Plus.
I am concerned that point loads from heavy furniture will irreparably crush the QFP as has happened with the existing carpet underlay. Would it be worth while laying anything over the QFP to minimise risk of this happening?
Also, would it be a good idea to relay the hardboard that is presently laid over the floor boards, to protect the SBM5?
Unfortunately, I must limit the net floor height rise to around 20mm. So cannot consider your thick floor solution.