Who is technically in charge of the Medics attached to a line unit?

So being a senior is a weird position bc yes ideally the 1SG will rate you bc you “work” for him, however the Med PSG is still responsible for your training and what you do medically so he will have a say. What I’ve found that works for me is I sit down with my seniors at least once a week and make sure I also communicate with the 1SGs to make sure we are all on the same page. I don’t task the seniors unless it’s related to their troops directly like SRP or shot rodeos. So for you the 1SG will write it, however you’ll want the MED PSG to have input so it doesn’t read like an NCOER for 11B SGT.

Are you assigned, attached on orders, operational command (OPCOM), or administrative control (ADVON) to the line unit? Is there a memorandum of agreement or memorandum of understanding between the line unit and HHC on the relationship. Start there.

If you are rated by the 1SG, then he is in a,position to direct you. If he wants you to report the HQ PSG for missions and taskings or Barney the Purple Dinosaur, as long as it is not illegal, immoral, dangerous, or just plain stupid, you do it.

I would have the discussion that for technical supervision you, as the senior medic present and an NCO, should be directing the medics.

This is always a fun issue because each unit will do it differently. Jeres an article tjat might help.
https://www.army.mil/article/203331/the_challenging_world_of_command_and_support_relationships