Hi Ian,
I'm not so sure that you'll notice the sort of difference that you did with your other cars such as your old Subaru.
Firstly - your 208 model CLK has seperate coil springs and dampers, it doesn't have the same 'struts' as on the other cars you mention like your Volvo.
Also, I'd imagine that your CLK is quite a bit stiffer than many of the cars that these braces are aimed at - such as jap stuff and hot hatches etc.
You'll almost certainly see more of an improvement with fresh OEM shocks and springs than with the addition of a brace, IMHO
Modification wise - perhaps performance springs/dampers, or thicker (stiffer) anti-roll bars etc might be what you're after?
Will