I took a quick look at what MyCanvas did with part of my family tree on Ancestry. Maybe there are formatting options I haven't seen. But on the standard 11" x 8.5" book MyCanvas created, the census image scans are formatted into a 7.8 inches wide 'window'. The widow height (3.3 - 4.7 inches) depends on the height of the image. So any census image (whatever it may contain) is going to cover no more than 70% of a MyCanvas page.
One thing I'd certainly do is to to crop (and straighten) your census images so that they contain only the 25 (max) lines of census data + header lines (Year, Town, district, etc.) that you want shown. In other words crop out any "wide black borders" from the scan. Crop out any Public Records Office Id strips on the right hand side if you don't need these in the book. You could even crop out blank 'white borders on the page. This kind of cropping makes sure that the 'image windows' in your book are filled with only relevant census information. MyCanvas expands the cropped image to fit the window.
Two examples below: one with the Public Records Office Id (as originally scanned). The other without the Id (as originally scanned too). The examples aren't very accurate. I took two MyCanvas screen shots, and resized them in Photoshop to 11 inch wide.
It's a bit of a puzzle because you ideally want to display all the census columns for your family. So the "width" (after cropping out borders and PRO Id strips) is pretty much fixed. Unless I'm missing something, the image width is going to be the same whether you display a list of 25 names or 4 names.
I'm not absolutely sure whether the larger book size (14" x 11") has a larger 'census data window" but I would assume so. It might be worth considering if you're concerned about the readability of the census text.
Mike