Match drilled form halves, screwed them together and sanded to profile on template. Routed top edge to 1/8" radius then sanded the 10 degree spring-back bevel around edges.
I used a left-over piece of plywood for backing form half which had defects in the side that I had facing outward. This side became the interface when I flipped the form halves inward. I'm hoping the voids do not cause any issues when forming the aluminum.
Since I do not have a spindle sander I improvised the formation of the crimp notches using a hand file and a tapered grinding stone in my hand drill. The results aren't as pretty or precise as what I'm sure could be achieved with better tools and set-up but the only true measure of effectiveness will be the results achieved when forming metal. If my rib meets design intent and looks good I'll stay with this method. If not I'll have justification for a trip to Home Depot for the Ridgid EB4424.
