There are three factors that determine if you can safely and easily use a 4-line bar from manufacturer A on your kite from company B. In descending order of importance, they are:
- 1. Are the kites from both company A and company B designed to flag to one front line, or to two front lines?
- 2. Do the bars from both companies have the Y-split (where the center lines split in a Y towards the kite) at a similar distance from the bar?
- 3. Are the line-to-kite connection points the same (loops vs. knots)?
has already talked about the the first factor, which is the most important one. You don't want to connect a bar that flags out to two front lines to a kite that is designed to flag out safely to one line, or vice versa (or you could be in for a nasty surprise when you activate your primary safety release).
In you case, you also have a problem with the 2nd factor: Where the Y-split is. This isn't as critical, but basically your kite won't fly as well if the angles at which the front lines pull on the kite don't match what the kite was designed and tested for. There is always some flexibility, because the angles will always vary a bit depending on how long your lines are, something that most manufacturers expect and test for. However, the North bars & kites are a bit extreme in that the Y-split sits unusually far away from the bar (unlike the Best bars & kites, which like most manufacturers place the Y-split much closer to the bar). So, basically, your Best Waroo probably won't fly exactly as it was designed to do if you connect it to the North bar.
The 3rd factor is just an irritant. Some companies put loops on all
line ends and knots on all
kite pigtails (e.g., Wainman). Other companies have "kook-proof" connection systems where e.g., the front lines end in loops and the back lines end in knots, or vice versa. So, you could find yourself in a situation where you are trying to connect a loop to a loop, or a knot to a knot. This can however easily be fixed, by e.g., adding an extra set of pigtails between the kite and the lines - just make sure that you don't accidentally make the front lines longer than the back lines, or the other way around.
In your case, the bottom line is that I would avoid using the North bar with the Best Waroo.