max size without top frame

Thank you so much for the response to our inquiry.
I will send more information and drawings shortly.
In the meantime, how wide can we go without the thickened top piece?
Originally, we had drawn a 3′-0″ x 5′-0″ tub. I would like to keep the size as close as possible but without the thickened top piece. At this size, how deep do you recommend that we make the tub?

I can provide some options to make the ofuro with a simple plank edge (without the need for the top frame border reinforcing):

1) using the 33mm thick planks: the limit is the S5 size:
S-5)  1300x750x640H (550mm internal): 540,000 JPY

2) increase the thickness of the planks to 42mm. In this case the border is not needed but there is a cost increase.
1500x750x630 (550mm internal) Hinoki tub : 950,0000. JPY

3) making the tub with your preferred size (5’x3′) and depth around 530mm is possible but we would have to further increment the thickness of the planks to t=50mm
1520x910x610 (530mm internal) : 1,220,000. JPY

Please note that the cost of packaging and shipping depends on the size you choose so it is not included in the quotation at the moment.

Please let me know of any problems or questions.