I’ve been using a technique to drill holes exactly where I want them. I match drill through a 1/8” piece of scrap aluminum. View the cross through the hole, clamp and drill. I like this method and do it when I can.
After the holes were drilled I went to work getting a good fit. This took time to get both forward and sides to fit flush. I used my strong vise and seaming pliers to pt angles where I needed them. It was frustrating but after a while I caught on and got the angles I needed.