Installing wood below the vapor barrier is not recommended.
Install rolled insulation from below. Once the insulation is in place you can purchase rolled vapor barrier material. The material is called bottom board but is a rolled product woven from high density polyethylene coated with a continuous layer of black low density polyethylene.
This is also install it from below, by stapling it to the bottom of the floor joist as you roll it out, overhead. The insulation is supported by the belly board below the floor joists permitting warm air from the floor ducts to prevent the plumbing under the floor from freezing.
You can find several types or a kit for your exact size home by searching for "bottom board" at The Mobile Home Parts Store
For details about installing insulation under a fllor, and important safety tips see How to Install Fiberglass Insulation and Crawl Space Insulation
, from the U.S. Dept of Energy.
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