We use a material called postermax & buy it from Sign Supply USA, give them a call & they will send you a sample. It does tend to scratch easily & take a bit longer to dry but we & the customers really like the finished products' looks.
Our contact is Aisha in Cleveland @ 800-545-7818, tell her In-Service sent you there.
oops, not sure if it's 16pt or not... not sure how to tell, but it is heavy duty stuff; perfect for posters.