I saved Prism's post for future reference. I don't use starch at all but in the kind of quilt I've just made, with lots of small "blocks" and sashings, it sounds like a great idea. I also didn't think about changing the presser foot dial but will keep that in mind. I said I didn't get my quilt "tight" enough, but I didn't mean taut or stretched. I just smooth it and check the back to make sure I don't have wrinkles. I think my problem was exactly as some of you have said: stretching while quilting. Mine was not terrible but I did have a few tiny tucks where quilting crossed which annoys me greatly.
Thanks to the original poster for posing this issue and to everyone who provided tips and helps!