I have no idea ,all I know is Bert made these floats in the 70s and they where spot on for the Blythe and as said rivers such as the Dane ,Wasn't the dumpy float one of Billy Lanes ie: Trent Trotter. Peter Drennan made them with polystyrine bodies. Used them on shallow River Dane swims.
Nick....with a little thought you can make yourself rattle and clunk free........but to me the biggest threat is footsteps and putting things down on the bank......even skylining if done very slowly has less effect than noise transmitted from the bank itself.A good read mate.....
like alan says,it`s a jigsaw with loads of pieces.
Without doubt this style of backbrook type fishing has to be my favourite,especially on the Ise (a little sister of the Nene).
The use of a stalking jacket was mentioned....i have a ron thompson one,with loads of pockets and zip on/off arms and a foldaway (in the collar) hood.I picked mine up for less than £20 on line last year.
My only complaint about these jackets is that you tend to rattle and clank a bit when walking up and down the bank because of your hooks and shots and bits and bobs being packed away in little plastic boxes etc.... not so much of a problem though when carefully placing your feet when watching/stalking your quarry.