Yours must be pretty bad, then. Mine only had a few cracks on the top of the upper hinge and was not sagging yet.
There is no inner structure to weld to, It is about 6 layers of sheetmetal bent over, folded and spot-welded from the factory where everything meets there (inner fenders, A-pillar, firewall, cowl support, dash structure, etc) that forms together make a solid post, unit-body style. Mine was an easy fix, but mine were'nt nearly as bad as yours must be. My repair has lasted over 3 years 75K miles and I hope yours does as well.
Maybe you can get up in there and brace it with some flat stock or channel iron.