I actually remember reading about the movie when it finally got its US release. I don't think that was until sometime in '71 though I think it was filmed in 1970, soon after John participated in hoDS.
Here's the ad (which I don't think I've ever shared) that appeared in the Boston newspapers on August 4, 1971 (the same day NoDS opened):Karlen also did an interview with the long defunct Boston Advertiser that became infamous in fandom in the '70s because many DS fans believed he said working on DS was working on "garbage." I have shared that interview before - but it was back in the VantageNet incarnation of the forum, so it's no longer available. But if there's interest to see it again, I'll try to dig it up...