Finally got around to having a longer look, with a lamp, under my right side front wheel well and found this.

http://postimg.org/image/8zwx1nc7f/

Of course the coating will have to come off but up by the vent (?) hold there seems a bit of corrosion. If this part has serious issues...what, exactly, gets replaced? Is that part of the fender? Part of the body to which the fender is welded?

You have a typical fiat problem. every spider i have ever owned has those cracks. That square tube is welded to the inner fender. It can be repaired without taking the fender off, but it is not easy. to get to the top, it helps to remove the headlight bucket so you can see. after welding, i put a light gauge angle iron doubler plate to span those 2 cracks. better check the other side as well.

Amazingly helpful, thanks much.