I would be stunned if the deck on my 99 Mobius floated. Looks like just molded fiberglass, couple of metal brackets, and the top pad. I think it would sink like a rock and not provide any floatation at any time.

As far as weight on platform... I would never have more than 3 adults on the platform - but I would expect it to hold that. We ski from a dock so rarely have more than 4 people in the boat - so who knows...