What about a minhag shtus such as g’brochs or not eating in the succah shmini atzeres? Or when the reason for the minhag no longer exists? Well you’ve got numerous g’dolim and poskim who will permit you to change; find one.
Being Machmir on Pesach by definition is not Minhag Shtus, even if the Chumra is Shtus. I believe it is a Noda B’Yehuda.
Not eating in the Succah on Shmini atzeres is a Minhag Shtus, but being that the Hagaos Maymoni (quoted by the MA & Taz) tries to defend it, we shouldn’t go there.