Gotta agree with mkseven on this one. 6 to 8 slalom sailors racing on a downwind M course is fast and furious

. Its hard enough keeping your place let alone worrying where kiters and their lines are. Most guys that I windsurf with are still pretty unsure with kites around so having them in a race situation would be downright scary.
Sailors entering gybes at 25 knots plus, round a buoy fairly close to one another is fun but fraught with danger.

Toss in just one kite (not 4 or 5) and this adds another dimension. When a sailboard crashes it stops pretty quick, when kites crash there seems to be a board (usually unattached), all that high tensile line and a big teabag at the end flying all over the place. Ive seen guys get dragged thru carparks, over fences and along the beach so add that to a slalom race?? No way.
This is not a flame on kiters but the 2 sports need to exist slightly apart from one another. My 2 cents worth.