Please tell me more about pillar bedding. What material should I use for this area? Can I custom cut aluminum pieces to place in the sections to stiffen it up before adding other material?

One guy I know suggested bondo with fiberglass in it for this area then seal it with a sealer. I'm going to tackle that section after I finish the action. Also, I'm not sure how far 4 oz of the Acraglas will take me starting at the rear of the action going forward.

On the Acraglas, how is the best way to remove the extra that seeps out or goes where you don't want it? I'm assuming file and sand paper?