I have a set of Barden's Two-Tone humbuckers on my Heritage535. They sound absolutely amazing, both in split and in humbucking mode. Bridge PU gives a very traditional LP-type sound (obviously, not exactly as we're talking about a semi-acoustic here) - OK, very Larry Carltonesque. Only problem with them was that the total cost (including shipping & customs) was £400. I'm still trying to put that at the back of my mind. The Mules I got from Tim cost just under £200. 'nuff said.