Blue Star Banner ????

I thought I would make a Blue Star banner for my nephews that are in the service, but have not deployed yet. Looking thru the different sites, some of them list sizes, others say there is no specific limit to how big, only to use a certain ratio. I thought I remember reading one pattern that made them about 20x24 or so, to hang in a window, but can only find ones that are like 8.5 x16, 8.5 x 11, etc... which isn't the same ratio's...
Is there someone out there that has made these by a specific pattern that can help me out? Thanks!