Agree with Jim , the JBWeld followed by the Caswell will work. Id be sceptical on the solder if its just adhered to the outer edges of the pin hole. You may have nothing to lose, but why not try a method thats gonna work for sure. Here is whats worked for me several times: Make sure you make those pin holes a little bigger, using a punch or small screw driver, you really want to find out how weak than thin the metal is around those pin holes. When I did my tank, I pushed the holes open wider/larger until I found solid metal. I sand it with a Dremel too and washed inside the tank near the repair area with acetone, being sure to remove any rust sediment that was there (or it will continue to rust). Once you have prepped it with acetone, you can also dimple the area around the pin holes so that it will hold a layer of JB weld better. Mix up some 2 part JBweld and push it into the holes so it extrudes into the inside of the tank a bit. Once that dries, I apply a short-strand resin based filler thats fuel and water proof. Once all that dries you can apply your liner.