Like you Don I've purpose made floats for many years, possibly slightly more than I've catching fish! I've probably made the lot over years from pole floats, sliders, wagglers, balsas, trotters, Trent trotters, sticks, Avons, and a few more besides. Still use my own floats a lot though not always. Like you I've sometimes perfected a float that couldn't be bought.
One little stick made from fibreglass and balsa was the best I ever used for light roach fishing, almost cried when I lost it playing a big chub.
I have made goose quill floats to Victorian specification with the whipped over quill and ring at the base using shellac, linen thread and old colour paints rather than fluorescents, and these were framed and sold by a local dealer though not claimed as old.
Once had a long conversation with Topper about his Avons. his are designed for very specific use, and to be used in a special way. From that I gleaned that changes to design could be advantageous for other conditions. I see a lot of Avons that are based on his design being used locally when a change to the shape of the body and length of tip would result in a better float for the conditions. His float was designed for deep slow water with upstream wind and only shotted to base of the tip. It is also a big float for long range mostly 10BB plus. Used one myself (home made) yesterday on lower Stour for bream.
Foe holding back, shallow water, or boily water you need a shorter tip and more of a shoulder to the float; goose quill is useful for really heavy water.