I suspect that most bowyers who make more than a few bows really don't tiller their bows for 3 under or split anyway. I think they tiller their bows for a certain preconceived tiller, like zero or + 3/16, which may be based on some testing they did once upon a time, or some information they inherited from someone or read about. Every bow is different, and if you were really going to tiller a bow for 3 under or split, you would have to shoot the bow until you discovered the correct tiller for that particular bow, which I guess is one advantage in having an ILF bow, because you could do this yourself even if the bowyer didn't have the time to do it. I would guess that 9 out of 10 bows I have had were easy to tune, regardless of whether they were “tillered” for split or 3 under. For the 1 out of 10 that wasn't, I either eventually figured something out or sold it out of frustration.