I read an interview with the bass player from Jimmy Eat World and he was going on about having left handed necks put on his custom shop P-basses...quick search laters:
Q: As far as your bass rig goes, do you use the same setup in the studio as you do live? I saw on a late night show that you used a Fender P-Bass with a reverse headstock on it. Do you use that one a lot?
A: That guitar came together, I guess it was a few years ago. I had it and the neck was broken on it, so I called up a friend at Fender, and he said, “Hey, you guys tune down a lot, right?”, which we do; we play a lot of the songs in C#, so he recommended that I try the reverse headstock. What that does is it makes the E-string have more length, and what that does is, it helps stabilize that really low note. Because before, and I had noticed this, when I’d hit the string and I was tuning, you can see the movement of the string would add tension and change the pitch of the string.
...so it was (apparently) a tuning issue. No idea whether there's any validity in this, you would also need to factor in string gauge...I mean would you tune a .100 or .95 to C#?
P