I did not send mine because i read in a couple of places that it can be sent at a later stage, at the same time you submit your medical exam, my reasoning behind it was the following:
march 10th --- I sent out the form (no fbi recieved / sent)
march 20th --- Letter from Canada asking to re-submit the application (still no FBI prints recieved)
June 1sth --- Recieved FBI prints, Resend application.
the idea is, i took a shoot and lost no time with it but i could potentialy win time if Canada allows me to send it later.. its a Win or stay even situation... does that make sence?