Our Caldera Martinique was delivered 8 days ago, and installed on a new concrete patio which is uneven to provide drainage in a particular direction. The installers wanted the tub to be level, so they measured a pressure treated board and cut it the same length as the support bracing built into the bottom of the hot tub. Then they spray painted it black to match the bracing, let it dry, and slid it under the tub. If you look under my hot tub, you can't tell it's shimmed because they went the extra mile to make it match underneath. Now the tub is level. Also, the installer said that little bit of lift will give water a path to run off and keep it dry down there. I know the Caldera manual warns against shimming; but this was the local factory-rep folks, who also provide warranty service, so I believe they know what they're doing. A guy I work with has a Hot Springs, which is shimmed in a similar way, and he's had no problems in the 3 years he's had it. That's my experience, for what it's worth. Good luck to you, whatever you decide.