Well, it makes sense that others have done it---it was only new to me! I should have known I wasn't exactly blazing new trails, but was so excited I had to post about it.
As far as the comment that these may be the same as 3-series sports seats, the M3's are a bit different in that they offer adjustable side-bolsters. I don't think the 3-series sports seats have that option.
I'll post more pics if anybody really wants them, or more explanation. Mainly just wanted to give others the knowledge it's doable.