You may have completely missed my point. You are claiming that the Mesorah makes it not a safek. But the safek that I am talking about is gufa whether mesorah discusses this issue. If you can’t prove that it does then there is a safek that it might not in which case we would have to wear Techeiles. So as I said, until you can prove that the mesorah is against Techeiles, safek d’oraisa l’chumra prevails.
Huh??? There are quite a few mesoras around today. I don’t think any of the R”Y or gedolim who are the primary bearers of them have any “sfeikos” about their mesoros. If your mesora says “don’t change”, for whatever reason, than you don’t, plain and simple. SDL has no place in that equation.