"Building an off-back set, but definitely ok with unique Piedmonts or Sweet Caporals." It is your collection and so whatever you say goes, but I would argue the ghost would have to be on the back of the card to qualify as a "unique Piedmont" in an "off-back set".
Brian may be a "T-guy", but I know he also looks at the "A":
https://www.net54baseball.com/attach...1&d=1666949495
https://www.net54baseball.com/attach...1&d=1666949498