Well, that wraps it up for my quest to clear GP 4 on all characters with default arms. (And motion controls, as always.) Ribbon Girl was the last: she was one of my best characters in the Testpunch and GP 4 was progressively becoming much easier for me with experience, so I went in thinking it would be a walk. I was wrong. Maybe I was just tired, slow to react, or otherwise off my game, but my first match (against Byte & Barq) took me about half an hour, leaving me bewildered as to why it was such a disaster.
It pressed me to change my play style quite a bit: I have a tendency to keep a distance and poke, and here I found that Ribbon Girl's aerial game wouldn't do the job as Byte still got a height advantage from jumping on Barq, and Barq would interrupt my rushes if I didn't take him out first. So I adapted to a close-quarters in-your-face style that also had the advantage of reliably keeping Barq out of action, but it took me many rounds to get there. (I don't think I'd drawn B&B in the first match before, and they seem easier to fight on their home stage, which is narrow and low enough to keep them contained. Couldn't count on that here.) This aggression worked for most of the matches from there, but I had to revert to my old keep-away tactics when I reached Hedlok, as I couldn't get in close.
I think the hardest thing to adapt to with Ribbon Girl after playing all the other characters is the lack of a mid-air charge. It's tempting to just punch in mid-air out of habit as she can bounce around so well, but it doesn't do much: if you want to go on the attack it's all about the fast fall. You can't initiate well from the air (like you can with Mechanica or Twintelle) unless you prepare a charge ahead of time.
After playing all the characters, I can confidently say that Helix and Ribbon Girl have the best sound clip on the "Thank you for playing!" screen: they both sing the opening notes of the Arms theme.
Anyway, I should probably buy some arms with the 892 coins I've banked up before I proceed to GP 5 or dabble online, assuming my arms aren't sore tomorrow from running the GP 4 four times in one day. Once I've decided which characters' sets to focus on first, that is.