Here is the best info I have on actual German canvas material. From a company brochure:
Gebr. HAPPICH GmbH
HAPPICH-Sonnenland
Cabriolet-Verdeckstoff
Their translation next to it:
Hood Material for Convertibles
Looking in a German dictionary, Sonnenland is two words, Sonnen means sun and land means land as in dirt or soil. Maybe the two combined make a new word but Babelfish translation says it means "sunning country". I have also seen the word Sonnendeck used.
All you need to know is that the material is actual German canvas as I am told there is only one mfgr of the canvas and they supply everyone.
As to who makes the best top? Since everyone uses the same canvas it comes down to the top makers pattern and their idea of what is correct. Before you buy a top, discuss it with the person that will install the top. Every installer has a preference. Currently, good tops are available from several sources, including GAHH, Robbins, Electron Top (for whom I am a dealer). I know these companies actually take raw bulk canvas and cut/sew the tops.
I will always give club members a great deal if their installer is comfortable with installing a top made by Electron Top. Just call me at 214-826-5977 and I will get you a current quote. As you can imagine, the cost will depend on the price of material from Germany.
I am familiar with the drumming sound but have never heard it in a Mercedes. Wet the canvas and dry in the hot sun, then drive the car to see if the drumming goes away. That's all the advice I can offer.
Will Samples