I install a Covermate III Lifter with almost every spa sold. It is a great hydraulic lifter. For 90% of our installations, the regular CovermatIII is fine, no extenders required. But, the Maxus, does have a large radius. I'm not a Sundance dealer, but it looks like a good choice to go with the extended brackets. They are just a little bit longer, to add support, for spas with a larger radius. You can also contact Leisure Concepts at 800-469-2428. They do not quote prices to the public, but they will answer all of your questions, they are familiar with Sundance Spas and which lifter will work best. Goodluck. Dave.