So, to follow up, the advice was good.

I asked nicely at the gate, GA was very accommodating and it all went well.

Even made it onto the upgrade list.

Funny side effect I hadn't thought through though - new flight put my following day TATL just over 24 hours out, so that hiccuped when I went into the lounge, but the attendant was very nice and waved me in.

Thanks for all the input y'all...