F-Secure as primary and Avast installed as secondary line of defense?

I have made a post on all the security problems I am having and since I already had AVAST lying around and after doing some research I found out it had a compatibility mode. Where it can be installed as the second line of defense. Has anyone done this and has it worked for them and finally does F-Secure recommend if possible to install other lines of defense as long as they are designed to be compatible. Thanks Very Much in advance, Rich Walston