Hi Dave,
Here's a quote from your last post: "You must be testing for image quality etc?" You are 100% correct in your assumption. Testing image quality on canvas become very expensive. I've done a lot of work on this subject and I have found that the Enhanced Matte profile renders an almost exact match to the Canvas profile when actually printing on Canvas. There is a very slight correction factor that I use once I get the results I want on the Enhanced Matte. This correction of course is applied in Photoshop, since I print mostly from PS. Of course you must also know that I am printing on Matte Canvas. Obviously the Enhanced Matte profile would not work very well at all with a Gloss Canvas. In the printer driver you can of course choose whatever printer profile you want and then set the media type to something completely different. They are independent of one another. For example, when I print on Ilford Gallerie Smooth Pearl I use the Ilford printer profile but then I set the Media Type to Epson Premium Glossy, following Ilford's recommendation. Another example - when I first started printing on Canvas the manufacturer suggested using the Epson Watercolor Paper Radiant White profile, since they didn't yet have a profile of their own that I could download. So this procedure is certainly nothing new. In the printer driver I also create Presets for every paper type and situation. That way I don't have to go through all of the steps that are involved in the driver every time I make a print. The Paper or Canvas Preset contains all of that information. I don't know which App you are printing from, but if it is PS then Presets are a must as far as I'm concerned.
Now to address the fact that I do indeed test for image quality on EVERY image file I print. Just a little bit of history here. For more than 35 years I have been doing custom darkroom printing for a variety of photographers and certainly a variety of work. EACH AND EVERY "negative" had to be tested before a final print was made. Even then, there were often times when the full print showed areas that required more work, so back to the darkroom. Of course with digital it's a whole different ballgame, and I can say without any reservation that I do NOT miss the darkroom at all, EVER! However, I will also say that no matter how well my display is profiled and calibrated, there is no way that I would go straight to a final full sized print without testing a section of the image first. Wasting paper and ink is not my idea of efficiency or cost effectiveness. With a well calibrated display and the proper approach to soft proofing the number of tests can usually be reduced to one or two, but on more challenging images there's no guarantee.
Now I'll try to capsulize my comments somewhat, since I feel I might have muddied the waters previously by offering too much information. I have found that as long as I have set the Media Type in the driver to Canvas and the Paper Type on the printer control panel to Canvas I have never had a problem with image length. As a matter of fact, it's always about a 1/16" longer than the image size I have created in PS and I am NOT adding any % to the image length at all. Personally I think that's pretty close. Use whatever printer profile you wish, but as long as these two settings are correct you shouldn't have a problem. If this procedure doesn't work for you then it's my belief that you are doing something different in the driver or on the control panel.
And again, on the 9900 the Paper Feed Adjustment will NOT fix this problem! That did work with the 7600 and I believe one of the later models, but not on the 9900. This has been substantiated several times on other forums. I had tried that initially, but to no avail. At one point I had the setting up as far as +70 and it made absolutely no difference, so don't even bother with it. Leave it at "0" and use the driver and control panel settings I have already mentioned. They definitely do work!
Gary