I did try a few times, but no human being. I also emailed a couple of days ago.
No response yet.
It's not that I haven't had luck getting some help from CJ over the years. They have indeed answered some of my questions! But given the responses can be a little hit or miss, and since I had the tubes ready to try, I was wondering if there was a quick answer so I could try them.
It turns out that the answer is complicated. I've decided not to try the 12AX7 tubes, to be careful.