Deck stiffening for houseboat on HDPE pontoons?

Hi all - this is related to my thread over in the Materials section but perhaps this is a better place for this part of it.

Given the lack of stiffness of HDPE, is there a general "best-practises" approach to designing a deck for a houseboat on HDPE pontoons? I'd like to avoid constraining the design of the superstructure, so I'd prefer not to make deck stiffness dependent on tying it all in together. Some sort of truss arrangement seems like it might be appropriate, more resting on the pontoons (with allowance for thermal expansion) than really tightly integrated with them. I'm even wondering if a heavy-duty version of some existing truss dock might be the answer, rather than coming up with something custom. Something related to this sort of thing (but with tubular pontoons for the reduction in resistance and the ability to tolerate being frozen in in winter):

Before I really get into it though, is this a problem that already has a good solution?

Thanks!

 

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