That was using the TetraMic into an R-44 (OCM), which was my only 4-channel recorder at the time. The mod simply prevented accidental mis-adjustment, it did not gang the channels together. They had to be set beforehand using a test tone and a meter, and if I had to change gain from that one setting I had to remember to re-do the process afterwards, measure the level difference between the test tones, and make inverse level adjustments to the files in an audio editor. My recommendation is to not use an R44 or any other recorder in which you cannot match and link the gain controls! It works and makes great recordings but is a major PITA.
Definitely use a recorder in which you can exactly match gains across all channels and gang them together to keep them that way as you make necessary level adjustments. Tascam DR-680 (either version mk1 or 2) and Zoom F8 can do that. Zoom F4 probably can too, I've not followed that one closely enough to confirm. Their may be others. Otherwise you'd need a audio interface that provides digital gain control and record to a laptop or other computer host.
I waited to buy a 680 mk1 until after the 1.20 firmware update specifically for this reason, and never again ran the TetraMic into the R44 after that. I love that recorder, just not for recording ambisonic A-format (native mic output) in a live music situation.