I don't think most string manufacturers publish their tensions specs, but maybe I just haven't bought strings enough lately.
In any case, there's no simple correlation between string gauge and tension since each manufacturer uses different materials, winding techniques, core wire diameter, wrap wire diameter, etc. Two strings of the same diameter can have radically different tension or two strings that have different gauges may have the same tension.
In any case, typically, lighter gauge strings will have less tension than heavier gauge strings. The kind of buzz you're getting would be the symptom of the new strings having less tension, hence the backbow in the neck.
If you significantly change the truss rod settings, it may take some time for the neck to reflect the change, so first, give it a little time. I think that tapping the back of the neck a little to make sure that the truss rods aren't hanging up wouldn't hurt.
If you still have a back bow with the truss rods completely loose, then you will need to have a qualified tech take a look at it. You may be able to correct the problem with a fret dress. Another alternative would be to return the instrument to Alembic for a heat treatment, where they warm the neck then retension it. In the most extreme cases, a refret might be required.
It's unfortunate that it turned out this way. Ideally, you would want to address this with a simple truss rod adjustment, but wood is a natural material and there's basically no way to be sure how it will act until you assemble the instrument and see how it turned out.
David Fung
