The reason they claim that the German bridge won't work is that they are formed to the top radius of the German bass. It's a simple mater to adjust them to your bass. Place a sheet of sand paper, maybe 220 or finer, sand side up under the bridge without strings,(maybe tape it in place to prevent it from moving and scratching the top). Then move the bridge forward and backward on the sand paper. This will make the bottom surface of the bridge conform to the top of the body.
This is the right way to make any floating bridge fit the top of your bass or guitar exactly...you get more contact between the bridge base and the top wood, and possibly improve the sound quality and volume a bit, too.
I have repaired several old archtop guitars and this is THE way to do it!