Some of you may have figured this out, but for those of you who haven't...
S-series of this vintage (maybe a few model years huh?) requires different size wiper blades. The Driver side requires a 25 inch blade, and passenger requires 27.5" blade.
They don't make a 25" blade refill...so ...
Get a set of blade only ANCO W-28R refills AND a couple of extra end-clip-thing-a-ma-bobs (they'll give you some if you ask - get 3 or 4 so you can screw up and still have some left) Cut off one of them by c.3" (measure with the blade in the wiper arm. Let exactly 1/4" stick out and whack 'er off with a hack saw or Dremel tool. Duplicate the little clip notch with a couple of 1/32 holes drilled and kind-of blurred together.
Mercedes replacement blades $60 ANCO blades $5
WORKS LIKE GANGBUSTERS
By the way...a tip for getting the old 'original type' blades off: Pull out the metal strips first...then the rubber will come off easy enough. (reverse is how you put them on anyway)
I hope this helps somebody.
Mims in Nashville