Dry clamping Top

I've struggled figuring out the best way to glue on the top. Initially I thought I would use my workboard and a cork shim as Cumpiano suggests. The workboard seems to have worked well for carving the braces, but isn't correct for clamping. The workboard is flat, but the top of the sides are shaped to the 30' radius; and the top braces are glued onto the top in the 30' sanding dish. So trying to glue the top onto the sides on a flat surface will not work. Even shimming the neck/heel block up 1/8" doesn't work right because while the waist sits on the workboard right, the space between the neck/heel block and the waist is unsupported and thus can not be clamped.
One alternative I've seen is to glue the top onto the sides in the go-bar deck, applying pressure directly to the top... but this doesn't allow me to align the neck as I want. To do this, the top has to be down and the sides on top of that. Also, but having the top face down, the seam can be inspected from the inside during the glue-up to ensure a good joint.
So, I came up with the idea of using a workboard that is only 5" (or less) wide. This allows clamping directly to the top around the sides where the profile changes due to the 30' radius.
You can see that the top is shimmed at the head/heel by 0.125" and is gently bolted down. There is also a cork cushion under the whole thing (minus the sound hole to see center line) to protect the top surface from being scratched. The workboard has a center line along the whole thing for me to align the top to. The clamp pulls the center of the top down and constrains it to the 30' radius shape. Next, I start clamping the sides (with the neck attached) to the top.
The wooden clamps have cork cushions, but the black clamps only had rubber feet so I added a cork cushion to the rubber feet. This method allows me to properly clamp the top to the sides at all locations around the rim AND I can ensure that the neck is straight with respect to the top.