Hi, I've got a 13m Bandit, which is really nice to use, but the lines are tired and has outdated safety. I'm looking for spare parts on line but not much out there. I'm thinking I could use my RRD bar/lines if I could even up the centre lines. I've measured the difference between them by fully sheeting in the bar, having the depower strap 'powered up' and stretching the centre line so elastic is at full (as it would be in flight?). I believe this is the correct way to do it? The difference I get is 2.4m. Outer line length is 24.4m. Centre 22m. If they were all supposed to be connected at the same point for tuning you could do so by extending the front lines.
I remember working in a kite school with those old F-one bars with the un-even line lengths...what a nightmare. There were virtually impossible to tune unless you knew the factory ratio between the length of the front and back lines... Perhaps you could chase that info by contacting F-one...
You're probably due for a kite/bar upgrade, but if you really wanted to use any other bars on your F-One kite and also assuming that from Factory the back lines are in fact 2.4m longer than the front ones, you would simply need to add 2.4m extensions to your kite's wing tips attachments. An idea that comes to mind is to grab one 5m extension line (Ozone sells those line extensions in a pack of 4), cut one in half (2x2.5m) and create one or multiple pig tails (figure of 8 knot) around 2.4m mark and then you can connect any even length bar to it.
You could then guess the correct tuning simply by flying the kite and see if it's underpowered or overpowered, but you would need some experience for this.