Hi Mike,
When I was still using the 7600 printers I always set the media type to Epson Enhanced Matte, since that's also the profile I use for canvas. That and a paper feed adjustment in the Epson driver gave me good results as far as image length was concerned(no canvas "shrinkage" issues). However, when I started printing canvas with the 9900 I had to try a few different approaches to get the image length to print correctly. Paper feed adjustment had virtually no effect for that purpose, so for a short time I was doing the ever so popular 1.4% addition to the length of the image. A bit of a nuisance for sure. I was also using the Enhanced Matte setting on the printer panel as well as in the media type. I then decided to try the canvas setting in media type and on the printer panel as well. That combination has worked well for the past few years. I do however still use the Enhanced Matte profile for canvas. I do all of my testing on Enhanced Matte paper, less costly that canvas. I then apply my correction factor from EnhMatte to canvas and the results are exactly as predicted. So to answer your question, yes, I do use the canvas setting in "media type" within the driver. I have no idea how the HP is set up, so my printer control panel setting is likely of no use to you. I use Breathing Color canvas and have tested their profile. The results were almost exactly what I get with the EnhMatte profile, and in some cases not quite as good. Although you are of course using HP, I hope some of this might be of help in your situation.
Cheers,
Gary