That's interesting, so the trim strap alone gives you the same range as 2-3 knots plus the strap on other brands?
The rebels have a good wind range using just the depower strap, in my humble experience.
Also you know once you get past a certain amount of throw the kite is already flying 100% on the power lines, there is zero tension on the rear lines.
So adding additional depower does nothing. On my C kite this happens after you throw out the bar about 3 inches, you can add as much throw as you like, the kite is not depowering any more than that.
You could add additional pigtails on your rebel to make the rear lines longer but I think it won't add any more depower than what the kite already has using the depower strap.