Sharee,
With a 3 1/2" dropoff over the length of the hot tub, your spa is danger of cracking. An acrlic spa is not made to bend. Filling the spa would not be wise. Many people make the mistake of just shimming the corners that are off 3 1/2". This is more dangerous to the shell, then leaving unlevel. If one side is shimmed, then the center footwell will be about 2 inches off the ground. Your Leisure Bay holds about 3700 lbs of water, not to mention the 800 lb spa weight. All of the water weight will gradually force the middle of the spa structure, to try to reach the ground. This will put a huge stress on all four corners and crack the spa. What must be done is a level sub structure must be built for the spa to rest on. This structure should be run the entire length and width of the tub. You are basically building a deck or patio on top of the sloped concrete patio. This can easily be built from wood, in just a couple hours. Pressure treated lumber would be a good choice or a resin type lumber. You can make the platform to be as little as 1/2" thick on the high side and 4" thick on the low side. You can cut down rafters from nothing on the high side, to 3 1/2" on the low side. Cut down 5 rafters and place them on your patio, space them about 16" apart. Then screw down pressure treated plywood to the rafters. Now you have a nice level 96"x96" platform for the spa to sit on. There are other ways of building a level platform. A leveling base could be made with concrete, stone, 4"x4"'s etc. The key here is to protect your new spa and provide it with the level base it requires. If you ignore it and the spa cracks, no manufacture will warranty it. Spend a couple hours to assure 15 years of enjoyment. Goodluck. Dave.
