If anyone is interested...............
If you search 'The Trent Trotter and Chubber by Billy Lane' which is a thread I started back in 2007, it offers a little more information on the float and how/when it was used. All of this based on info from the Billy Lane book Peter mentions...Others, including flightliner also offer alternatives on the same thread, all of which might help the OP.
I did eventually get round to making some of the Trotters based on what the book told me and in similar materials AND from additional info offered by another FM'er who sent me additional measurements. (Cannot recall who it was, though!!).
Anyway, well worth the OP getting hold of the book if possible.......
Hope this helps - someone!