Buy Coro made for printing, it tends to be flatter and prints better... It costs a bit more, but it's worth it when you're not rejecting 50% of the Coro.
We buy from laird - they use a brand that's made in canada... Not China. They talked us into the China stuff once and all the corners were bent, it was the thinnest / weakest shit we've ever used...we told them even though the Digital/Canada stuff was 40% more.... Never send us the China garbage again.
We pay $14 (cad, $11 usd) a sheet for it... And can sell it for $100+ once it's printed on, no reason to buy the cheapest garbage you can get.