Before you go running out twisting things I thought I'd chime in. I own two 300SD and have adjusted both with no problem. I have also gone to the local u-pull it yard and scavenged up a few spare ALDAs. Inside are two well constructed brass diaphragm chambers. They look very tuff. I have removed and inspected over a dozen ALDAs and have yet to find more than one thin copper washer. ( I found the same thread you mentioned while contemplating making the adjustment) One car is adjusted full out with the boost at 14psi and smoke is all but undetectable (only visible in following head lights at night) The other is 1 1/8 turns in and smokes lightly under full throttle.
To remove the ALDA I have had success with a medium sized crescent wrench and a firm grip on the ALDA. The large nut underneath is captured on the IP, turn the nut clockwise and support the ALDA with your free hand. Do not allow the ALDA to turn too far and damage the plastic vacuum control valve
I hope this Helps, I say go for the gusto and turn the little screw out.