Bringing the cap home required applying a dead-blow hammer to a large piece of wood against the rear cap at the lower cross bar. About 30 good whacks on each side did the trick. Here it is in place with all the bolts tight. I then went around the sides and riveted the edge (in all the old locations plus a few new ones). I still have to rivet the edge of the roof, apply more sealant, repair one corner, re-attach the drip rails, seal them, and probably cover the roof seam with adhesive flashing for good measure.