I've tried to tune to standard with EJ38's (.10's) and I definitely noticed the top and bridge lift. Is this normal? Will the bridge eventually lift off?
WHAT YEAR IS THE GUITAR?
Guild's build techniques and undoubtedly other things like bracing changed over the course of production on those.
They alternated through periods of "built like a tank" in mid '70's to early '80's and periods of "lighter" construction, particularly in late '80's and again in mid '90's until '01, but the F512 was called the JF55-12 during that period.
I have a buddy, original owner of a 1987 (first year) JF30-12, he experienced bridge lift after less than 2 years.
In that case it may have simply been a flaw in gluing the bridge, which is its own known "problem"***.
But in any case ever since the repair he's tuned tuned it down at least a 1/2 step and used silk and steels besides, which I only recently discovered were the original spec for those (JF30-12).
Sure it's not the same model exactly but same body size, and similar construction characteristics will apply.
We've recently seen evidence (owner's manual) that Guild
did actually suggest tuning down in the mid-seventies, "IIRC" about the era; but later, by the '90's, was Guild was ok with standard tuning, but had gone to the EJ-38's (.010-.047) Cougar mentioned.
You certainly can't go wrong with those EJ-41's but if you still get bridge lift I'd wonder why.
Will the bridge eventually lift off?
*** AS noted above, yes it's
possible but not inevitable.
Guild was unusual in that they didn't install bridges until after instrument had been finished, which meant that there was a masked off "glue pad" left unfinished on the top for the bridge, and the finish extended underneath the edges of the glued-down bridge, creating potential area for the bridge to pull away from the top.
I can say that I've seen far more stories from 12-string owners here of keeping their guitars at
standard without problem, than vice-versa.
And of those who
do tune down they frequently cite tonal rather than durability reasons.