Just be careful with the carpet pad, especially if you want to "do it right the first time" because carpet pad will rot under your liner after contact with moisture in the ground. Even with sand under it, it will conduct moisture from the ground underneath. I am also in Minnesota and I know that with the winter/spring thaw cycle, the ground will move a bit and moisture will wick up. At at some point you will no longer have that padding there. You can get overnight on the Happy Bottom or other appropriate materials from several merchants and it is manufactured to be used under a pool and be in contact with the moisture. The carpet padding does work ok under the Intex Easyset and Metal Frame pools because they are not permanently/long term installations so the pad is stored for the winter/spring thaw. JMHO -