Jill: THe correct answer is NO, on anything that is classified as oversized letter ( which I believe equals about a pound in American measures) you do not require a Customs Declaration form to be attached to the outside. I can be 100% certain of that as I work for the CCRA ( Canada Customs Revenue Agency) in enforcement and compliance! Even though I am in currently in the Taxation division, did my time on the Customs side as well

Hope that helps!

Michael Behiel