interesting thought coop, i like the sound of that!
could i add to that suggestion, for what i believe are good reason.
Its well noted, that suds, sprints, and even comparitvley lardy 33's, that have been used for racing, have many times previously had rear disc conversion, only to find that they are so overbraked, they have the rear/front brake bias in the off or very close to off position, the rear ends being so light, even a mild improvement on the drum brakuing effort,can be too much.
so we know its not worth having dinner plate discs and six pot calipers, great, thats just saved a fortune too eh!
i very very much appreciate you are doing this for aesthetic reasons as much if not maybe more than any other, and to some that may be a little off the mark, but hey, i'm not some, and once i've done my own front end brake mods to my own sprint, i'm sure to be thinking the very same thing as you, so i'm with you all the way mate
so thats a long way round getting to the idea that has been buzzing around the old bonce for a short while, and could well work with the turned down drums into hubs idea, not overbrake the rear end, be cost effective, and look super trick.
my experience around the race bikes and autograss cars has lead me this way, so what about something like these single discs, just £34.00 a pair,
autograss rear disc.jpg
or something tricky like these waveys, at £60 the pair,
rear disc wavey.JPG
and then some super super trick calipers, like these Suzuki GSXR front Tokico babies, £89 the pair buy it now!
which being radially mounted, should make fitting them even easier than traditional adapter brackets required for the normal 90 degree side mounting, and whilst uneccesary, improves braking efficiency further too, which may be useful anyway with such small pad contact,
so, whilst i know hydraulic handbrakes are available too, i don't know the letter of the law regards mot?
but what do you think coop?