AGD, do you know how involved the band was in WIBNTLA? For some reason I've always thought of it as something Dennis kept private, but that's really only because of how the song is never mentioned by the band, or folks who were around at the time like Jack Rieley. I have talked to Stanley Shapiro, and what he said seemed to imply that no one around Dennis believed in what he was doing, aside from Brian. Was it that Dennis kept the music he was doing to himself, or that the rest of the band was trying not to be involved with him? There are a lot of stories of the other band members being 'jealous' of his talent, but I've never found that to be a very believable story.
You can hear Brian, Carl and Mike singing on it. So they were involved to that extent.