The green beastie has been sat for 2 1/2 months before firing up for MOT and I would say it had sagged a bit but nothing to somebody that don’t understand it
I left door/bonnet open when battery in place and engine start for a few minutes but it sorted its life out straight away, so don’t know if any air was left in the tank.
My one on Arnott Gen II's does not drop unless there are big temperature changes, the other one on new Dunlop bags drops about 5mm in 24 hours but never gets to the bump stops.