I got fed up with flat slide tpas leaking ,even after fitting corks cut from solid cork out of a bottle of wine.
I found port corks work best ( or perhaps it was the port )
The problem is modern taps are barrel plated so there is a ridge on the slide where there is no plating.

Original solution was to buy some brass BSp end caps then drill & tap them for a modern tap from Chinese chook chasers which are $ 10 a piece with free postage
Being small & not plated they are less obtrusive than taps for more modern things like A 65's

Down side beiing cast zinc they are corrosion sensiive to water and as I found out, will break ig you drop the tank & it lands on the taps, which of course happened just before a rally

So the "temporay fix" was a needle type filter for stationary engines on one side ( only had one ) and a bolt in the other.
This temporary fix has been in there for 5 years waiting foe me to refit the BSP to metric adapters & a ew pair of Chinese taps , which use the same rubber seals as Honda lawn mower & stationsry engines do so is easily rebuildable and is totally unaffected by long periods of standing.

I get better results from my taps since I've made a point of using both of them. I used to use one & neglect the other with predictable results. Using one, & then the other on the next ride keeps them in better nick.