About the thickness of planks

My current ofuro is constructed with is 41.39 mm and you propose 33 mm that is 8.39 mm thinner.
From your experience is 33 mm sufficient?
The next size we use for planks after the 33mm thickness is 42mm.
In case of a L=1200mm tub, unless for design reasons (beefy look) the
client asks for thicker planks, 33mm is more than enough.
Thinner planks will result in a lighter tub (which is easier to handle
at the time of assembly and maintenance/cleaning under the tub.)
Also thinner planks are less prone to cracking due to dryness.

We use a top frame construction for tubs longer than 1400mm and 42mm
planks for tubs over 1500mm.

Anyway, for your reference I prepared a quote in case of 42mm thick planks.