I didn't think that the window slot would move as much as it did when I started tacking the door cap metal in place. Tacking these took a lot longer than I thought it would because of all the movement and the tight fit of my metal cap pieces but they came out really nice and the metal fit is perfect.

I'm still deciding whether to weld the cap on complete, I know that welding it completely will warp the whole door top but tacking it allows me to work one end then go all the way to the other end which will keep the heat down.