On top only. Bare metal to metal contact between strap and frame, doors etc. Then mold the sealant over the top and around the joint, then clear coat. Or paint then clear coat. I put nylon braid around the strap and heat shrink tube both sides to seal it. Looks good and keeps the strap like new as well. I will post pics after work so you can see what i am talking about
Im looking forward to your method. Getting too old to crawl under truck.