Presented for your consideration...............
I have a late 60's - early 70's model A558 Aria classical that needs a neck re-set. This model has a dovetail joint I've been told. I've re-set a similar, same era and label, model A556 that has an identical body other than the solid cedar top, and it has a dovetail.
These 2 pictures I took before I loosened the fingerboard extension. I used a 24 inch ruler. The ruler dove down to just touch the top. The bridge is not the original, and has been shaved and the saddle lowered to allow lower action. The strings needed to have ball ends added to keep the break angle manageable.
But when the extension was heated and loosened to the 12th fret, the angle changed. It decreased.
Hi again John, looks like you're making good progress. my comment would be regarding the bridge. You say it is not original, and to me, in the photos, it looks like you may need to give it a good look over, would be a shame to have it fail after all the neck work you have done.
I could be wrong, but if that is that the proposed height of the saddle. I have seen bridges fail due to the saddle being too high above the bridge. this can cause a lot of forwards torque at the top of the saddle, due to a steep back angle pushing and the strings pulling the saddle forward. This can cause a lean of the saddle in a shallow slot, or worse pushing the front of the bridge out, as in my photo.
Also, check if the tie-block s strong enough to handle a steep break angle, if there is one, not much meat above those string holes.
But you will be the best judge, you have the guitar in front of you.
Time to put a bow, or at least a set of strings on this question/thread. Never came up with a reason or explanation for that neck angle change. Such is life sometimes.
The lowered non-original bridge showing in the pictures has been again modified. I've added two rosewood strips to restore it to the original height. This holds the saddle properly for now as I hunt for a new bridge. Looking for a replacement that is similar to original or something that catches my eye. But since it's my guitar, I can wait for now. The guitar has really begun to open up again after being played for 3 weeks as a practice loaner to a visiting classical student. I'm happy with my results for now.
Thanks everyone for your insights.