A massed rank of ?

What is the plural of Mercedes-Benz (which I have just this moment learned that Mercedes-Benz itself (the company) wants you to put a hyhen in)? This occurred to me as I read Shamini Flint's first mystery novel, Inspector Singh Investigates: A Most Peculiar Malaysian Murder (recommended, btw). Singh is from Singapore, sent to Kuala Lampur to keep an eye on the interests of his countrywoman, former super model Chelsea Lieuw, accused of the murder of her Malaysian husband, Alan Lee, who had just executed a master stroke during their custody battle: converting to Islam and declaring his sons Muslim (Moslem, she consistently spells it). This meant that the Syariah Court would decided who ended up with the kids...

At any rate, back to the topic at hand. Here's Singh, arriving in Malaysia and finding a taxi to take him to his destination:

Singh strolled over to the massed ranks of Mercedes Benz and climbed into the back of the first one.

I am not really sure how I'd pronounce that - both ways seem wrong now - but I would definitely write "Mercedes Benzes". (I think that's how I'd say it, too.) But English orthography is conflicted about final -S or -Z names. Some, such as the CMOS, say at -es for all of them, some for all -Z but not -S that sounds like Z (so, Davises and Rodriguezes, but Jones and Chambers (for Mr Chambers & family, as well as Mr Chamber et al) ... OTOH, we certainly "keep up with the Joneses" and the stupid spell-checker doesn't want a plural morpheme on any of them.