Here's a photo of the unique 'ballast' components for the Wildfire. Although I think the Maruader?? of the same era had a similar system.
On ebay, the seller leaves the following description:
"The designs main feature is the the low tech hollow keel through which weighted bags are lowered. There are 12 bags in all each weighing around 10 kg each. The keel is dropped down through a hatch and the hatch secured. This system makes the boat extremely stable and means she sails more like a keel boat."