Your primary concern with an over-sized* American flag is storage. It’s one thing to cover the front of your building, mother-in-law apartment, or used sofa pile with a 70′ x 90′ American flag; it’s an altogether different thing to store it, safely and legally.
After observing proper folding techniques, it would still result in a coffin-sized section of cloth and would as such, overpower the conventional, “one garbage bag and then into the attic” approach. The obvious next step of two garbage bags, one coming from each side with a slight overlap, still fails with a flag of this size. A crucial midsection would remain exposed to storage mites and closet fleas.
Patriotic ingenuity points us to a three bag solution. Before fitting on either end bag, a simple scissors cut turns garbage bag three into an open-ended garbage sleeve, able to slide freely over all sensitive sections of the flag. Loading this first, then tucking either edge under the end bags ensures total coverage, total peace of mind.
At this point one may safely store an enormous American flag alongside spare mattresses, under model train sets, and beside inherited wig collections, confident that no portion is exposed to the tentacles of those translucent creatures that are found only in crawl spaces.
*Some prefer the descriptor, “American-Sized”, improving it to, “American-Sized American Flag.”