I haven't made any big prints with canvas yet, but have put some cut down A4 sized sheets through to generate a custom profile.
I'm using DaVinchi Matte canvas and it seemed to work very well(Using the Watercolour paper-Radiant white option, with a paper thickness of 5 and a wide platen gap). Although it took a couple of attempts to get it to feed properly from the rear manual feed slot, the printer saying the paper was skewed, but that may be just poor technique on my part.
Once the printer had 'grabbed' the canvas there were no further problems.
I'm hoping to make some proper prints in the next few days and will report back.