i can speak from experience, 1 materia v. 4 materias on gear didn't increase my SB rate - I spent 3 weeks crafting off/ on with my CUL hat - the first time HQ with 1 materia, second was a nearly max melded hat (because I now have my artisan specs) and both took the same amount of synths. I can confirm they still SB faster then my very first CUL hat with no melds, but the amount of materia did not seem to make a difference. I can also confirm in both cases where I was SB melded gear, I was crafting the same amount of high level foods.

Hope that helps, and GL with your SB'ing.