Silicone bronze technique for structural integrity

[Schroeder]

I'm going to weld the lower quarter seam to the rocker on a 77 trans am today. I want to fill it with silicone bronze. I've never done that before. I cut the flange off the new quarter since it's otherwise inaccessible for welding with the outer wheel house already installed.

Do I need to put some strong tacks in place to structurally hold the panel in place and then fill the gaps and any recessese and go over the steel filler tacks with silicone bronze to ensure it doesn't pop or come loose later?