I like the smell of new canvas (or old canvas for that matter). Canvas would be in keeping with the vintage of the trailer. However, it is not waterproof. You would need a ridgepole of sorts to keep it elevated and off your load. If the canvas touches anything while wet, it will transfer the dampness. With the old military style tarps, the rope can be woven from grommet to grommet so that it forms loops to pull down over the hooks. One pull on the loose end and a knot will cinch it down tight.