There is a build on the 'nets that has a piggyback...but the reserve was shortened/modified so that it wouldn't hit the downtube on full compression. I couldn't find it just now, but I'll keep looking.
EDIT: Found it:
https://www.mtb-mag.com/en/dream-bik...r-all-country/
Attachment 377575
Attachment 377576
Pretty sure I wouldn't build it that way...but SUPER swanky, for sure!