Spacecrab,
My disclaimer first: I'm not a metallurgist. That frame looks lost. When rust sets in from the inside, it's difficult to treat. This is your CJ-3B? There should be some drain holes down near the pivot attachment. I don't remember if you've posted images before of your w/s frame but if you've got a good amount of holes to allow moisture in, this could contribute to rusting inside. Once those drain holes are plugged once established, it may be very difficult -- if not impossible to stop what you have.
I've got a set of top bows where the bottoms are rusted off. I'll have to cut upwards until I get good metal to repair. I assume that's what you'd have to do here also; cut off the arms a little at a time until you get to some good metal to attempt a splice-in repair. That's assuming you want to or can.
The only other suggestion I could offer is a replacement. Where are you again?
**Added: I struck through the drain hole comment. I can't find any on mine so this may be misleading.
