Both Ross (p161) and Gould (p195) are completely clear when they say that the left hand end of a tuplet bracket aligns with the left-hand side of the first note.
However, LilyPond doesn't always do this - instead, if the first note has an up-stem, the bracket is aligned with the stem instead. Is there a reason for this? And is there a way to correct this globally, or do I have to tweak shorten-pair for each affected instance? Paul