Im making a banner for a customer and it is gonna be pretty big. the dimensions are 43.5 in x 64.5 in

Their printer said that it just needs to be delivered at 300dpi CMYK color. ( I already know what the safety borders/bleeds are) That is all fine.

My question is that iv never designed something for that big of a print. What size should I be making my canvas in photoshop cs5..the full size of the dimensions? Somebody mentioned cutting the size in half in photoshop and just raise the dpi to 600. This is a bit confusing. Just not sure if the canvas can bee smaller to make it easier as a file to work with. What would you guys set the canvas size to so that when it goes to print at the dimensions above it will look good?