I think Stevie wrote most of I Cant Wait. She tells the story of Rick bringing her the music and her staying up all night writing a song to the track. Its a classic Stevie song with her singing about herself in the third tense and then singing about herself in the first tense. As she calls it...her Bob Dylan
I cant picture anyone singing I Cant Wait except Stevie for that reason.
Stevie and Rick were friends as teenagers. I think I heard her say that Rick was Robin's brother best friend.
I cant picture Stevie singing "I get weak" either.