Conditions for the Cape Point Challenge can vary hugely, so giving a definitive reply is impossible.
As an "out and back" type of race you're generally going to face both upwind and downwind conditions, so a versatile ski which can handle both well is a good idea.
One of the biggest challenges of the race is the reflected chop off the cliffs which you will most likely encounter at some stages of the race, and these can create havoc for less experienced paddlers. Be prepared for confused sloppy seas with waves and chop coming from all directions, and look for a ski that is comfortable in unsettled choppy seas. If possible, try and get some practice paddling close to a rocky shore with reflected waves, its quite an art to master.
Good luck, its an awesome experience paddling around Cape Point in a ski!
