Yeah, It's about cut out materials. I am asking because I have never seen a letter fomat in my life. :D Got no feelign for it. If A4 is widespread n the US I will just go with it. And ignore letter until there is demand.
Yeah, A4 is hard as heck to get in the states unfortunately. I think you can get it at specialty paper shops and japanese bookstores, but other than that, I haven't seen it. I would just put safe areas on your prints so they can be safely cropped to fit both paper formats.
