The "shrinkage" issue is not limited to Lyve or printer model , ie Epson 9900. The shrinkage issue is something that can effect any poly cotton canvas, and especially after coated with a water based varnish/protectant. Shrinkage generally is only in length (not width) similar to when washing a new pair of Levi 501 jeans. The difficulty is that shrinkage varies among individual printers themselves, and a singular answer is not always applicable across the board for a single printer model, e.g, 9900, 9800, etc.
The "canvas" setting in the Epson driver does help, and for some this may address the shrinkage issue completely. This is a relatively new setting that I believe Epson has tweaked to address the shrinkage issue, and basically only for newer printers (9900, 9890, et al). I would NOT adjust the feed settings on your printer as this really is not a print quality issue, e.g., banding.
For older printers, you can figure out how much "shrinkage" your printer does for a particular size of canvas. If it is "short" you can figure out the percentage of shrinkage, and then adjust only for that dimension percentage using the image size function in Photoshop. You will need to make sure you print the image in that adjusted direction only. Not difficult once you figure out the formula.
A really great printer utility that specifically addresses this issue is Qimage. Because the shrinkage issue (I call it the Seinfeld George Costanza effect---"it was the pool!") varies with individual printers, Qimage lets you dial in a specific percentage for the printer utility to adjust the print image for shrinkage in the length direction only. Simply Awesome! For example, my 9900 still has very slight shrinkage even with the canvas setting selected. I simply can dial in a small percentage of shrinkage into Qimage, and the printer utility takes care of everything. Once coated, my Lyve canvas prints are right on.
p.s. You can get a custom icc Lyve canvas profile made using color targets using the "Canvas" setting as opposed to WCRW.