Hi Mex,
I own a quiver of XR4's : 7, 9 and 12. Wind range is exceptional on all kites and IMO as good as wind range can get. The 12m gets me going upwind on a hydrofoil in as little as 7 knots with longer lines and in about 12-14 knots on a small twin tip in flat water, probably need 15 knots in open ocean (I'm 85 kg)
I can hold the 12m in 25 knots, it's harder to boost high in those winds with a large kite but you get impressive hangtime with 4-6 seconds jumps easy.
On a twin tip for boosting sessions, the 9m starts to be fun around 20 knots up to 30 knots and the 7m for anything above that.
The 7 and 9m are boosting machines and got me reaching heights of up to 12m (measured on the Woo) and hangtimes just under 7 seconds.
With a good technique and in any winds above 25 knots you can easily boost 10m jumps with 4-5 seconds hangtime consistently, without much effort.
Pro's kiting alongside of me with Woo's and C-kites outboost me in height by a few meters but they have less hangtime.
So in summary a perfect kite for your intermediate to advanced booster who likes long floaty jumps, old school tricks and soft landings.
A friend of mine took the 7m out in 30-35 knots and thrown some decent kiteloops followed by a downloop with controlled and soft landings, impressive!
The kites are super stiff, unbelievably stable and very well built. Additionally, the new Core Pumps makes pumping kite soooo easy and fast you don't mind so much changing kites when the wind picks up or drops off. You can pump a 7m in 20 sec. 9m in 30 sec and 12m in 40 sec. I don't think electric pumps are that fast.
Happy boosting,
Christian