I've had atleast 4 body men tell me that a hood couldn't be seperated like that then welded back together. They say the heat will warp the skin.
Most said "just by a hood". One old school body man used a marker to outline where the understructure could be cut and welded back thus avoiding the perimiter spot welds and heating the skin. In the end he said the same though, "just buy a hood".
I know this didn't answer your question but I really would like to see your proving them all wrong. Good luck