Yeah, I waitd too long on this one. Probably could have avoided problem if I noticed a few yrs ago and drilled some drainage holes and covered it with oil or grease periodically.Have tried both the "naval jelly" type of remover and the "converter" type, with long term unsatisfactory results for serious rust. I'm always amazed at how oil or grease slows it down though, assuming it's an area you don't need to paint and look good. In Sweeden, the old Saabs regularly went in for a spray of the underbody with oil. As to the battery box area, I've seen rust-out there in the 740s, for obvious reasons. Strangely, the frame member on that side of my car is perfect -- it's just the driver's side that has the problem. I'm going to get some estimates this week hopefully, and I've heard you have to remeove the computer(s)to avoid damaging them. thanks again for the info, jim