You cannot disable solid collision for 8 direction objects in any easy way, to let them wrap. There are how every plenty of other options for you. I took the liberty of coding up an example for you using the bullet behavior as enemy control (you can slow down the speed and make them turn towards an object to have them more like ai-enemies. This way you have the option to let them Bounce of solids or simply let them pass. I also added the wrap behavior to them. There are quite smart things you can do with the Sine behavior which I've learnt during the past years. I'm not really sure it will suite your needs (I just guessed given the bit of code and sketchup I saw). But I've added two sine behaviors to the "cannon" one for the horizontal movement and one for the angle movement.
So hope you get something good from this