but in dini momoinois minhag hamedina takes precedence over halacha.
Not really true. It does in examples where the item sold is unknown (like Mocher Shor, or Tzemed), but will not wave chovos.
I think what you mean is Dina D’Malchusa. And even there, I believe it is questionable at best if DDM will apply.
Ask your LOR.