Maple has diffuse pores in its grain structure, so as far as stability is concerned, it does not have more flex in one direction over another. Most vintage instruments were Flat Sawn, simply because of the availability of wood in the ’50s and ’60s. A byproduct of this is there are plenty of people who feel Flat Sawn sounds better or feels better than Quarter Sawn. There are also people who feel that Quarter Sawn is punchier, and some companies are praised for using straight Quarter Sawn lumber on their necks. My opinion after building guitars for 40 years is there is basically zero difference. Quarter Sawn has a slight advantage in that it is more dimensionally stable in the width direction. However, we dry our wood very carefully so this is not an issue. With roasted maple, none of it matters.