Thanks guys - I am a little confused, but I will study the link and I may head back to re-assess it.
I made an offer on a D55 on reverb, but was rejected. So, still guildless ... for now.
I appreciate all the help!
NO snark intended, but back to
combined bridge and saddle height:
1/2" of string height above soundboard, at the front of the bridge, is a very common standard to ensure that there's enough tension exerted on the top for good energy transfer from the strings while still allowing for reasonable action height at 12th fret.
So bridge height is ideally around 5/16 and saddle height around 3/16, subject to "tolerance" on both of 'em. Add those heights together, you get your ideal 1/2" combined bridge and saddle height.
When Guild set necks, they had bridges ready to install of various heights, and would select a bridge that matched the neck angle after it was set.
The point of Frank Ford's tutorial was to show how to check that the neck angle is properly aligned with the height of the bridge, but the bridge must be of appropriate height for that alignment check to be "valid".
Here's why:
Ideally you want a straightedge laid along a neck to line up perfectly with the top of the bridge. You can then adjust saddle height to achieve the desired action height at the 12th fret.
BUT a straightedge that's starting to collapse into the top will wind up extending to a point
below the top of an unshaved bridge.
IF the bridge is shaved though, the alignment check will look "good" even though the bridge and saddle aren't actually tall enough to put the optimum amount of energy into the top anymore.
The height of the saddle is relevant because the angle of the strings over it ("break angle") also affects how much energy is put into the bridge and thus into the top.
So a "low saddle" could be a sign of compensating for a collapsing neck or simply somebody having lowered it for a really "slinky" playing feel with very low action on the neck.
The only way to know for sure about the health of the neck though, is to do the neck alignment check.
(Although I guess if you find that action at the 12th fret is also very low, like 3/64 on bass E, that would be an indicator that the saddle was lowered for a player's taste instead of to compensate for action getting too high from neck collapsing. As a neck starts "going south" the action gets progressively higher and harder to play, that's why a shaved saddle CAN be a "danger sign", and it's easier than the more radical shaving of the bridge.) .
Guild's spec for action height at 12th fret in the;'90's at least was 5.5-6/64 on bass E and 4.5-5/64 on treble, which some people do find to be a little high for their tastes.
But if the saddle's very low like under 1/8" tall AND the action's still too high at 12th fret that's definitely a red flag.
A shaved bridge isn't a disaster but it may and may be prone to cracking. In any case they can be replaced, but with a shaved bridge the instrument's tone and volume are compromised to some degree at least, and chances are the neck will continue to collapse to a point where shaving the bridge and/or saddle no longer restores playability.