Lots to think about on floating roofs.
There are external floaters and internal floaters.
I have many spreadsheets that I have build over the years and they are all a (work in progress).
There are single deck and double deckers?
Internal pontoons or pan only.
Give us a bit more info and will see what we can do.
lgwsaw is right there is a lot to consider in the floating roof design, it includes single or double deck, or is it external or internal floating roof.
If it's internal, aluminum may be a better choice - corrosion, cost, safety, can suspend it from the fixed roof, storage, etc. May be worth considering.