What string gauge originally came on the fg150? I kind of like extra light strings on my guitars. Does it really matter other than sound?
I have no idea what they used back then, but I'd assume they were an equivalent of today's Lights.
I use either Elixir Nanoweb PB lights or D'Addario EJ16 PB Lights.
Using extra light strings isn't going to do anything another than making the sound thinner. 40-50 years of string tension pulls the neck up resulting in a bad neck angle. Typically the only solution is a neck reset to fix the neck angle.
I think I have a FG-170 with mediums on it for the last year or 2. I have to see how the action is, how much the neck has moved.
