I feel your pain with the rot issues.
I recently had to cut out and fabricate the rear spring holders and part of the chassis on my terrano.
Also over the years iv'e owned it the whole of the rear floor pan has been replaced along with inner and outer sills,inner arches,parts of the bulk head,front floor and inner wings.
Not much left of the original metal work
Quite a few times iv'e thought about giving up and sending it to the scrap yard in the sky