don't know if can help. I'm a little bit lighter (62-64) and till a couple of weeks ago i had an ozone c4 5mt year 2010 and was using it with a 45cm bar and 20mt of lines.
It was my kite for really gusty SW New Zealand's days. I think it had a pretty good low end. I think with 25 knots i could ride it with a wakeboard with bindings and i never hit the high end. As example one day i was on bindings while some beginner were out with a 12. Not best session ever but i still could manage to go upwind.
Several times with strong and gusty wind i saw 80 kgs guys with 7s going out from the water cos was too gusty for them. Under nuclear gust i was just boosting but otherwise i could unhook and do kiteloops (hooked and unhooked). What i can say to you is that i never feel i was too overpowered.
Now i don't have it anymore as it exploded after an attempt of a too radical kiteloop
I'll miss it.