I owned 3 Vincents in the early 60s , a Comet, a Rapide, and a Lightning,
at the time i read up on just about everything there was to read on them and i am fairly certain TVOP was not used in any of the motorcycle engines.
However, the HRD engine ( later to become Vincent ) was used in powered gliders during WW2 so it is possible these engines ran on a paraffin mix.
Back in 60/61 a fellow impoverished aircraft apprentice ran his Ariel side valve on aviation kerosene, he had to use petrol to start it but once running turned on the kerosene, it did smell a bit, but as we worked and lived near Heathrow nobody took any notice of the smell.
My knowledge on this is limited but what ou have all said does match with stories my dad told me of motorcycling during his days in the RAF with V squadron bombers in the 50's
I htink these days though with all the electronics and egr's and turbos and stuff caution is the word with any modern engine, when thinking about alternative fuels!