IoC - Never lose control over your base

After doing a few Isle of Conquests I decided to arm one of the cannons on top of the towers. I noticed how the west cannons (Base's point of view) can be directed into a small part of your own base. When aimed correctly you can hit the GY flag, making it nearly impossible for enemies to cap your base.

Here you can see the blue pilar of light, this way it's very easy to aim at the flag.



Move around with the camera for a bit untill you can see the flag.



I've been doing this for two days now, horde will come up only sometimes, if it's melee, you can shoot at your own cannon and kill it, if it's not you're going to have to deal with him yourself.

If this is just common sense, ignore my post, but I have yet to see someone else doing it. And I figured this is not how Blizzard intended it. Also I don't know if this works for Horde aswell.