For what it's worth, the chain stay holes on most bottom bracket shells I've messed with (30x16 type) don't even come close to matching up with the stays themselves. I blame the stays more than the shell but regardless, a lot of stay manipulation is needed to get a decent fit. I made a couple of wood cradles that can be used to crush and squeeze the stays in order to get the proper shape for clean plug in. I also try to fatten up the cross section as much as possible to resist sideways bending. At the end of the day a small angle misalignment at the shell is the least of my worries.