"He who marches out of step hears another drum." ~ Ken Kesey
I think a bunch of us use the same 15x20 envelopes from uline. I use a wire hanger under the flap and hang on a curtain rod. Got most of the idea from Alan, but have definitely seen others post about it. I searched for traditional large format hanging folders and couldn't even find 11x17 let alone 13x19 or larger. Not to mention, they don't make filing cabinets or insert systems large enough.
I think it's actually called the Jalema system Steve. We use the same thing here.http://shop.blueprintfiling.com/Jalema-Racks-Carts_c3.htm