I used Liquid Nails to fill in holes, corners, and screw heads prior to applying the Permadri. Do you think there's any advantage to using Bondo? I think that VLDesign met with some problems with Bondo on both his builds. Liquid Nails is easy to work with; just squirt it in and us a putty knife to get any excess and you're done. Hard as rock when you're done too.