I have also heard of 1" for each foot, but never heard of the speed thing? But thats not saying much on my part! 
I added some bracing  on my conversion, but only because I was nervous. I have sen others with nothing? 
Your right that there are not many I/O CC out there but there are a few.  I was just saying if you can find a nice I/O or a Seadrive they are the best to convert!
