In preparing individual instrumental parts for band and orchestra music both as a composer and a copyist for a number of years, the vast majority of my output has been printed (in the US) on letter-size paper, 8.5x11 inches. This is easy because it's a standard size for paper and printers. I don't need to special-order paper or use a fancy printer.
I'm fortunate enough to have a work commissioned by a more prestigious orchestra, due in a year or so. I don't want to sound like a novice, nor look like one. So here's the question. Do large regional orchestras in the US expect 9x12 "concert" size instrumental parts, or have they succumbed to the convenience and money-saving letter-size parts? Is it necessary for me to find a print shop that can obtain this size paper to put my best foot forward? Or is it something that no one will notice or care about, and a needless expense?