[AC Ventura]

It seems clear you need to try the spacer idea, as its simple and clearly other guys say it works.. However, if that doesn't solve it, then it means your near static fuel is most likely boiling in the line to the carb, once the engine is shut down. When it boils, AKA Vapour Lock, it creates an air pocket that can in effect, stop fuel getting to the carb.
One way to overcome, is to set your bonnet open slightly and alter your radiator fan, so it stays on longer after shutdown. Renault did this with the little 5 Turbo and it cured the hot start issues, which originated from a sometimes red hot turbocharger.
However, the bulletproof method is to have a return line back to the tank from the carb, with an in line regulator. This way cool fuel from tank is constantly circulating at idle and can't boil.
As with all fuel line fittings, monitor tightness regularly as failure of these is what causes engine fires. Metal air filter elements are better too.