Aside from the way Dorico handles sizes, if you are looking for a good large format printer I can recommend a used HP laserjet 5200 DTN or something similar.
These are reliable workhorses that can handle up to 12.5 x 18 inches, and if you have the DTN duplexer, it can print in duplex as well which is a nice feature to have.
These used to be pretty expensive but if you shop around on ebay you can find good used ones for around $500, maybe a little bit more for a refurbished unit. Toner is expensive (and I would recommend buying original toner from HP), so that is one thing to check when buying pre owned. Also it is heavy (over 80 pounds) so shipping will be $$$ unless you can pick it up locally. I was fortunate to be able to pick one up in SF a couple of years ago, paid around $375 I believe.