​270mm/10.5" and it is 670mm/26" wide.  The next one is 565mm/22" and 1220/48" wide.The rest is 770mm/30" high, less a bit where the tender hulls protrude​.

That is strange - on the 360 view the width of the platforms seem to be about the same or do you mean that the second platform is 1220-670= 550mm wide on its own?

I am curious how the platform ends curve up. next a 360 of the bottom ;-)

To prevent wave slamming against the lowest platform one could eliminate it and keep roughly a similar interior setup having a 565 mm platform on either side of the "through" instead. This complicates somewhat the windward side adding a platform there but simplifies the lee side having one platform less but both are on the same plane. With the "through" more in the middle there is more shoulder space too. That is under the assumption that there is less wave slamming at 565 mm height windward than at 270 mm on lee.