Hi Mike
I have installed inertial reel harnesses to my 7A slider.
There are a several styles of harnesses that you are able to use but the one I would recommend is a locking style and five piont. They have a cable attached to the reel that will lock the reel and stop it from rotating. I still intend to install a hooker style harness for areo's and only use the inertial for when i do cross country.
I consulted an engineer about the structural changes needed prior to installing the reels, I have had to add a 7075-t6 angle across the channel that supports the seat backs this also severs as a mount for the reels. New gussets were manufactured also. In addition to this a chrome molly tube needs to be fitted to route and raise the belts closer to the top of your shoulders. This prevents a downward load on your shoulders in the case of an accident. I have yet to do this but intend to manufacture a new seat back from chrome molly tube and incorporate this into it.
I will try and get to the hanger this week and get some pictures if you are interested.