No extension will be provided by CIC however you can make a cover letter point out the documents to follow on a later date,try to submit the maximum along with your RQ, usually PCH and CBSA traveler history will be in mail with you within 3-4 weeks. Talking from my personal experience. And in a RQ these two pieces of information are very important. If you will delay submitting your RQ, your appliation will be considered as abandoned and the file will be closed.