There was a 3 disc set devoted to Zinman's tenure in Baltimore called the Zinman Legacy. It included a Mahler 6th with three hammerblows. However, they were amplified with a degree of reverb for a very unusual effect. It's like a nuke going off. It's almost a party record for Mahler fans because they're so over the top. While they are NOT the dull thuds that Mahler wanted, I stubbornly believe that Mahler would not necessarily be opposed to the technology.
He's done it this way as a guest conductor, too, as I think Barry will attest. My friend who attended the Peabody Conservatory in Baltimore during the Z-man days dubs them "Praxis" Hammerblows, in homage to the planet in Star Trek VI that blows up with a tremendous shockwave blowing outwards.
I had some hope that Zinman would do it again in his Zurich cycle, even if it was as a bonus track. But only because I want the craziness in even better sound. It's probably not right to make light of Mahler's darkest symphony, but even though I think it's a funny effect, I think Zinman seriously thinks they work. So, I have to at least praise him for thinking outside the box.