Whilst you might be able to re-use the tubes from the inflatable, I'm really not sure that it would be viable. As far as I can see it would mean designing the hull to fit the tubes which is really the wrong way round!
I would guess that the cost of the aluminium hull would be far greater than the price of a new set of tubes, and re-usung them might be a false economy.
If you've got a hull in mind, then I would try the various NZ RIB manufacturers and see if they would make a set of tubes to suit.
John
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