So I think the cat form can certainly give him the stability that many tender owners find important. Even that little Zap cat can give good stability.
Now imagine the 'floor/hull' of the tender is nothing more than a flat plate,...pretty easy to fabricate from say a flat panel of nidacore with a suitable skin on either side.
Then why put somewhat complicated and expensive 'inflatable tubes' at either side?? Why not solid foam tubes similar to the foam collar material utilized on the 'SAFE boats'?
Then couldn't those foam tubes be provided with milled channels that would slide over the special configured ends of the flat panel floor board. Designed properly you might not even have to glue the foam tubes on, but rather secure them in place with 'commercial grade velcro' (interlocking mushrooms).
The size and cross-section of the foam tubes would determine buoyancy ...and load carrying.