OK, but FWIW, you'd be amazed at how much air can leak around a theoretically well sealed driver........... Regardless, 'Dull' tends to be too subjective a call for many, so I still recommend you get a true snap switch to test with. Mine's from a long gone/lamented '55 A-H 104M, but can be had off most any British car at least through the late '60s and if none is available from the junkyard, then they use to still sell cheap knockoffs at discount auto parts emporiums and hardware stores around here.

GM