If you’re storing flat, you could use anything with a bit of weight placed on top to help hold it flat. You can get a pre-made shelf from your local home improvement store to help distribute weight over the whole face of material then put the weight on top of it. This way the edges beyond where the weight is placed won’t still curl. Just thinking out loud here.
Two of the casters have brakes so some of that tendency to “swing” is taken care of, but I’ve thought about not using the casters at all since I dont really need it to roll around, and that would lower the whole cart a few inches.
I opt for a standing working position, trying to get away from being seated so much (25 years at graphics workstations - ugh). Standing next to the cart and placing a cardboard box on top to approximate the total height, I think it will be fine. Actual working time at the machine is limited, but being able to keep your back vertical instead of hunched over a table top height is much better for you ergonomically anyway.
The only height concern I have is the weight of the GF itself makes this top-heavy so I might shorten it based on that, in which case, I’m covered between having Sawz-All, band saw, chop saw, cut-off wheels and die grinders, or plasma cutter. Lots of ways to skin that cat.