Doh!

I'll stay after class to write "read the post, then respond" a hundred times

What I do is hold the ALDA case with a big c-clamp while loosening the retaining nut since I didn't have a wrench slim enough to fit with another wrench on the retaining nut. If you do it this way, pad the c-clamp jaws so you don't damage the ALDA.

Sixto
91 300SE
87 300SDL
83 300SD