When it was free I made the plugin required to integrate aiContactSafe in sh404sef.
It is still in the current release but some people seams to have problems with it. Others are using it and seams to work fine.
After it was made a commercial extension I didn't had access to it ( sorry, will not buy it just to create the plugin for my free extension ) and the guys that are developing sh404sef seam to think it is not possible to integrate the 2 extensions anymore. You can search their form about this discussion.
Maybe they know something about their extension that I don't know.
If you have a license with them I suggest posting on their forum with a link to this topic. The integration worked before.
I can't post on their forum because it requires a license and as I said will not buy one just to support their commercial extension. I hope you understand.