a scant (2) years later, and my rear SLS is now as it should be.
the culprit? the actuators / struts. (it's always the last thing you check...and, it's not ALWAYS the accumulators).

found a guy who was selling a pair of low mileage struts for $100. took a gamble and bought + installed 'em...and she's driving like a dream.

just goes to show that the struts can (and do) seize.
thanks for your efforts, fellas!

__________________
-lee
'83 300CDT (286k)

former proud owner of:
'85 mercedes euro 300TD
'80 mercedes 300TD
'77 mercedes 280e
'80 mercedes euro 250
'82 mercedes euro 250