The tricky part is that the frame rails are 16 gauge and the connector is 3/16".
First time I spent to much time in the center and blew through the frame rail. I ended up starting the puddle in the center and rolling it out to the connector bracket, then rolled it back into the center. That kept the puddle moving and without blowing through. And I could see the bracket melting into the puddle so I feel good about the penetration.
Then I ran a bead all around the edges.