First everyone can splice lines it's easy you just need to learn and you only need some thin wire (I use picture hanging stuff) and scissors to do it.
The only difference between a pulley bar and an ozone turbo is the pulley in the center. Interesting idea that and it should speed turning even more! There is no reason you can't make that either! but you'll need to add a safety to it!
Yes knots are fine if the line is overrated (generally thicker) compared to the other parts. 40-50% reduction in strength is a good guide so knotted line should be twice or more as strong or thick.
The most important thing when making a safety is that it flows cleanly through the bar enough to disable the kite. To do this you want it as clean as possible avoiding any knots on any part that slides THRU the bar. Knots below the bar where you attach a leash a perfectly fine. As well knots at where the line will stop or to act as a stopper are fine though they are annoying as they create tangles. Much cleaner to use a splice high up and a small diameter stopper/line guide at the bar like flysurfer uses for that.
Macisback wrote:will the front lines be used 50% when steering this way? (Can that ratio be influenced?)
Not sure what you mean. The front lines work as a point for the pulley to pull the rear lines against. Your hands still do all the work though the fronts do carry load. At some point the load between the front and rear lines will balance and you will pull on both. Like this the kite may not reverse( it will stall down though). So to relaunch you will probably need to be able to reach PAST the pulleys and actually grab the rear leaders to relaunch. That's a important design criteria so keep the pulleys as LOW as possible. The top of the floats should be fine though.
Macisback wrote:can I build a pulley bar that doubles the way the steering lines move without the front lines being used for steering too?
no, but there are other adjustments that affect turning(and other things) like wac, diablo line, mixer type, camber and span changes.
Macisback wrote:Last but not least would a Turbo bar work, or does it offer too little safety/depower?
Yes but you still need a flagging line, which I see the ozone doesn't have so don't buy that :-/ A fifth would be easy to use on a turbo, I am sure a front line safety could be used but would be a bit more tricky it looks to setup.