On mine (Juliano's kit), the upper attachment is backed by a plate with a welded nut. The recommended procedure was to tack weld (or tie) a piece of coat hanger to it to help get it into position. Once the bolt was started, I wiggled the coat hanger enough to break the tackweld and got the coat hangar back out.
The access behind there is tight and at a little bit of an angle so I don't think that something non rigid like a string will help much. It doesn't just hang down. You sort of have to push it at an angle. But using the string as a safety might not be a bad idea.
If you have a wife or kid available with a small arm and hands, they might be able to reach down in there and hold it in place.
