My cousin that bought my Cobra did that and he also got under his trailer and sealed between the floor beams. He said just making the bottom flush and smooth made almost as much difference as the added nose aero set up he built. His trailer is a larger one than yours, but he said his mileage went up by about 3 miles per gallon with what he did. I believe he used light fiberglass for the front and thin ply wood to seal the bottom.
Ron
