Ok, I don't usually get involved with this discussions, but since I love Sadowsky basses (owned several of them, still have one), I'd like to give my 2 cents concerning the issue "action not low enough",shimming, etc:
(disclaimer: IME/O)
1. file the bottom of the saddle so the string can go low enough.
This is the easiest, but the one I like the least = the break angle behind the saddle diminish creating a potential loss of down force and possibly thinning the sound.
2. shimming the neck.
This is the most common way with a lot of related misconceptions and drawbacks/neck deforming risk = most install the shim all the way to the bottom of the neck pocket - towards the bridge side - creating a high risk that in few months/years the neck develops a 'sky jump' at the last frets - been seeing this too many times. The right way (IME/O) is to install the shim where the two second/last mounting neck screws (close bridge side) so the pressure is on top of the shim and not creating a void that can flex.
3. filling/sending the neck pocket on the body (most expensive of the three).
This is my favorite way, it is permanent, but who's gonna reverse to a wrong setup? What I do is to create a tilted/slanted neck pocket surface so the neck sits tilted/slanted in respect to the body. Best contact surface - no void under the heel and no risk of sky jumps. It can be sanded to create even a little more action -raising that is - at the bridge.
Well, there you go
M