Desert Fox,
I think you are handicapping yourself needlessly. I am not a lawyer, but I am involved in law enforcement and what you say about blades >6" and possession of OC spray is only partly correct - the wrong part.
Neither OC spray nor long blades are restricted or prohibited in Canada. The applicable charge used for people who carry these things is known in short for as "Possession - Weapons Dangerous". The relavant section of the Criminal Code of Canada is here:
Possession Offences
Possession of weapon for dangerous purpose
88. (1) Every person commits an offence who carries or possesses a weapon, an imitation of a weapon, a prohibited device or any ammunition or prohibited ammunition for a purpose dangerous to the public peace or for the purpose of committing an offence.
Punishment
(2) Every person who commits an offence under subsection (1)
(a) is guilty of an indictable offence and liable to imprisonment for a term not exceeding ten years; or
(b) is guilty of an offence punishable on summary conviction.
The key factor for culpability here is whether your possession of the item was dangerous to the public peace. If you're carrying a big knife or OC spray in a populated area where there is no justifiable need ("justifiable" to the courts, not you), you can get dinged on this charge. Arguing they are for self defence (ie: repel attack by human) is NOT justifiable. On the other hand, postal workers in the city carry OC for protection against dogs. This IS justifiable.
If you are in the back country, I don't see that either a big knife or OC spray would be found to be dangerous to the public peace. On the other hand, if you walk into a department store with either on you, you may well by-pass the checkout line and go directly to jail.
The 6" blade rule is a tool used in law enforcement (probably based on old case law) to determine whether the knife by itself is "dangerous to the public peace" in a non-wilderness setting (ie: would the average person be alarmed to see this hanging on someone's belt). In reality, if you have a knife with a 3" blade and are handling it in such a manner as to alarm the local population, you could probably be convicted of this, regardless of the blade length.
In closing, the above is my understanding and experience with Canadian law on these issues, but I an NOT giving legal advice. Check with a real lawyer if you want to be sure.
Sorry for the long winded response. I hope that helps to clear this up.
Source:
http://laws.justice.gc.ca/en/c-46/41698.html