I'm new so I'm sure I'm missing maybe two thousand years of discussions about card stock and centering rings. But...whereinhell do I get card stock like Estes/Apogee uses for centering rings? Other than paying too much for it and shipping at Apogee. I know bunches of people use mat board but that stuff is lousy and separates ridiculously easy. I could use balsa, I know, but I do like using the card stock. Anyone have any idea where I can get it by the sheet? And not some little 4" by 3" sheet.