Hi Prawnhead,
I'd love to when I get the chance, problem is chances are few.

I think it could be fun in anything from 10-15 knots, after that, it may be a handful on a surfboard.
This is a hard pullin' kite and is probably better suited to twin tip freeride and freestyle type riding in lighter winds (8 to 18 knot range). Not to say it won't work on a surfy.
Problem with surfboards and light winds is the downwind turn when on a wave. The kite will get you out there in as little as 6 knots provided you are going crosswind or upwind, but as soon as you turn the board downwind, ie, to travel along the wave downwind, you will easily travel downwind faster than wind speed making the kite fall.
Although this kite will fly in as little as 4-5 knots (relative), that is the minimum wind speed needed to keep the kite in the air. If you ride downwind at 6-7 knots board speed, then you add that on top of the minimum wind speed needed to fly the kite and you get a minimum theoretical wind speed of 10 knots at the very least and more likely 12 knots to have any success at keeping any kite in the air. This is why no one makes a surf style kite bigger than 12m, there isn't any point.
The XR LW will work great from 10-15 knots where other kites will struggle as you take into account sweep or side shore current which further complicates the apparent wind problem.
If you don't understand apparent wind, come along to our free DIY bar tuning night next Thursday 31st March, where amongst other things, I will explain Aerodynamics and apprent wind as it applies to kiteboarding.
Minimum wind speeds for the Core Riot XR LW for me:
Race Board : 6 -17 knots
Twin tip 135: 9 -19 knots
Surfboard : 7 -15 knots
DM