The compromise that defines a foldable bag
A foldable shopper has to open out to useful capacity and fold down small enough that someone actually carries it. Those two requirements pull directly against each other: lighter fabric packs smaller but carries less, heavier fabric carries more but stops being pocketable.
State both ends of the requirement — the load you expect and how compact the folded state needs to be — and the fabric weight can be set between them rather than guessed.
The fold is part of the product
How the bag folds, and whether it stays folded, is a construction decision rather than an afterthought. A bag that needs two hands and a diagram to repack will be used once.
Check the fold-down on a physical sample yourself, several times, after the bag has been loaded and emptied. Folding behaviour changes once the fabric has been creased in use.
