Uh oh, well, ChiliD can probably explain this best so I'll leave it for him but I will say in the meantime that many FM fans need to recognize that the Mac are a band that had at least 2 guitar players (even THREE at one point) at most times in their history. In fact, it was actually odd for them to have only one, the Lindsey era was the only time in the Mac's history that had just one guitarist save for the HAHTF album on which it was only Welch but that was understandable in the wake of the bogus band situation and wanting to quickly try to rebuild the band's reputation and they may have also worried about trusting a newcomer at that time too. So the question really should be "Why only one with LB?"
Anyways, I'm sure ChiliD will be along soon to bring you up to speed on "Why 2 after LB?" though.
John