The review here is written from the viewpoint of either cruising or racing the boat two up, or rarely with more crew, mostly Round The Island (of Wight) races.

We have two children ( March 1998 and September 2000) and when we are sailing this means we have effectively 1.5 crew. One helming, the other rushing about.

It is definitely possible to hoist a spinnaker with 2 crew and recover it successfully without the need for a snuffer. Short handed on Wednesday evenings racing it is often the case .

General Sailing

The boat is responsive to the helm, never being particularly heavy even when heeled, although there is some weather helm when beating. The rudder appears to be the same as some other 29 foot Westerly with a transom hung rudder, as it is listed in spare  part lists under the same heading, at about £1400 ! So repair rather than replacement seems to be the order of the day. 

The helm tends to need fairly constant attention or an autopilot because the hull does not have a great deal of inherent directional stability, although it is possible to lash the helm for brief periods.

Off the wind it can become more of a handful, a beam reach with spinnaker often resulting in holding the helm hard over to hold off the broach. Letting the main out or the kicker off controls this.
More experience with the boat allows one to feel the beginnings of a broach and stop it. It seems less on the edge now at high speed.  Having a full crew when racing holds the boat more upright and in control.

A check on how close you are  to hull speed is that the cockpit ends up at about sea level at high hull speed , with water just washing the Treadmaster if the boat is level. A tubby crew can make this worse !

I have never been out in more than a recorded 35 knots of wind, in Southampton Water in the GK24, when reefed with 2 reefs in the main and a 100% genoa. but others have had to manage 50 knots off Brighton and lived to tell the tale. 

The GK24 is definitely a sailing boat, because of its Quarter Ton racing ancestry. Because of this it has a relatively large rig compared with other small boats. Our fractionally rigged boat has 35 feet of mast.

It is necessary to reef earlier than these other boats to turn down the power. In lighter airs, It is faster than many other cruising boats, even 30+ footers.  You can literally sail in circles round Westerly Centaurs in a light breeze.

When you first step aboard, the boat heels quite noticeably, but then you are over 4 feet out from the centre line. Under sail, with main and No. 1 genoa the boat heels noticeably to the breeze but can easily hold full sail up to 15-18 knots apparent. With crew ballast the limit is higher. In an extreme case, I have feathered up in 30 knots of wind without the main flogging, in a sudden gust.

Genoa Only Performance

As this is more manageable we quite often use this configuration for low-intensity sailing in stronger winds. We don't have to deal with the mainsail trying to blow away  We hoist a 100% jib/genoa and sail slower, or motor-sail.
Recently we crossed from Hamble to Cowes in 27 knots SW wind  average, 32 in the gusts with a 100% genoa up and no main, and still made to windward.
In this configuration, the boat will stop if the boat is first feathered up into the wind to lose way and then the helm pushed down to 45 degrees or so. The boat moves
very slowly to leeward and forward. Ideal for waiting for shipping to pass in the Solent.

On another occasion we were lazy and sailed in 20-25 knots of wind with only the 135% genoa up. 

We had started up off the wind but eventually we hardened up and we were still making to windward and overtaking other boats. As the wind gusted first there would be lee helm due to the off balance sail plan and then weather helm as the boat heeled. Once I got used to it, it was OK but it took concentration. Putting up the main would have been easier.

GK24 Squall

I have been in a squall which took the boat over to the point where the cockpit coamings were stopping the sea coming in.
The wind was blowing 11 knots from the beam, and we were lining up on the start line for a white sail reach with 150% genoa and full main on a Wednesday evening race.
We were looking at  boats around us rather than behind us. Not may were near us fortunately ...
As the gun went we were hit by the squall. The boat went over, and I am sure that one crew member was hanging on mostly to the  spinnaker winch on the high side of the cockpit and not much else. I dumped the sails and still the windage was holding us over. The rudder wasnt doing anything much, as it had lost its grip on the water. 
So I leant forward and  released the genoa halyard, partly dropping the sail,  and then we came upright. I remember looking at the mast while the wind was howling and thinking that it was making an interesting S shape against the line of the forestay, the flogging sail shaking everything violently.
We re-hoisted reduced sail and continued to the first mark. Nobody else was with us as they had been put off by a Westerly Storm 33 whose mast had folded in the squall. So we went home and as the murk cleared we saw the Inshore Rescue heading off to tow the Storm 33 away from the lee shore which they were headed for.
Of course I had a novice crew and I did have to reassure them that yachts don't capsize...

Reaction of the boat to waves

The boat will point all over the place when rolled by the wash of a power boat, but if you hold the helm firmly it ends up mostly back on course, although a little worrying at the time.

Because the boat is not very long, the problem with progress is rapid pitching in a choppy sea : the Solent is full of power boats and tidal races that stop you dead in light winds. In heavier winds, crew on the rail make a huge difference. Out beyond the Needles the wave period is longer and the boat begins to ride over the waves without stopping or losing much way. Out there we can overtake boats that leave us standing around the cans inside  the Solent.

It is easy to stall the boat, even ending up going backwards after hitting a wake , so one has to free the sheets and bear away for speed before hardening up again. If you don't, the hull just makes leeway. In this respect it is like a performance sailing dinghy.

In waves, spray comes over the bows, but they usually lift over the waves (fast pitching!!), and so the occupants of the cockpit are showered rather than drenched.