I began the modification to the bottom cowl to allow for the a/c compressor. I want to avoid the unsightly bump that so many builders seem to accept in order to accomodate these compressors. I've also seen the same on a few alternators, primarily on the early -4s and -6s. I applied two staggered layers of 1/4" foam in an area large enough that I'll be able fair in the the mod to the existing shape of the bottom cowl. I sanded the foam to shape and then applied a very light filler to blend in around the compound curves of the cowl and the foam edge. After all is dry I will sand the filler to shape and add cloth.