Kicking this around gives us a feel for what it most needs; first up a pair of wing-spars. I've extended the laths around the back end to suit, and up front I'll drive a dowel ~ or in time be carbon-fibre rod ~ through each lat and boom to maintain a level profile.
Intend to reduce the seat-back to make it flush with the decks, and I shall probably leave the 'parcel-shelf' off too because it's me who gets to say so.
Also I shall reduce the size of the seat by around half to effectively shift it forward, and cut the foot-rest in half to raise it clear of the waterline at a comfortable slant.
We're able to do that too because with the wing-spars in place the parcel-shelf and foot-rest are not so essential to lending a virtual box-section to the centre structure.
Want each pontoon to be a separate module ideally, with own motor and ancillaries.