Thanks Adam. To be honest I think there are probably better ways to get optical ttl if I want it. And as I will probably replace my housing with something else which allows more camera functions to be accessed with better ergonomics this will probably be when I can get sttl on the inon if I decide I want that feature.
You mention the battery drain and flash recycle time using optical triggering as downsides, but are there other disadvantages of this method?
I currently have the camera flash in manual mode at 1/128 is that a good starting point?
I found a thread on here detailing an electro/optical convertor, but it looks like the guy who was making it stopped production owing to the difficulty of coming up with something that would work with every camera/housing combination, there was another one too, but that one seemed to not get even that far.

