Bikepacking bag mount on Seatpost

Has anyone used a mount attached to the seat loop strap slots and around the seat post for a compression-style stuff sack on a Brompton?

https://qunature.com/products/waterproof-lightweight-bikepacking-tail-bag-extension-bracket-adjustable-rear-mount-for-long-rides

It would be feasible but not sure how practical if the seat post needed lowering. I think the Brompton could go into kickstand mode. This mount could be used for camping gear stuff sack, etc.