There is sufficient information to allow you to source your own materials and build the boat from scratch. However, if you then decide to purchase the kit the cost of the set will be deducted from the price. A good hard-chine hull tracks well yet is very maneuverable. The underwater profile of a hard-chine kayak changes dramatically as the boat is leaned. They are willing to trade some nice handling characteristics for slightly better efficiency.
Initial stability is often a bit lower than hard-chine hulls, and turns require more lean.
Multi-chine boats are more difficult and time consuming to build after all, they have so many more parts. Since they have many seams, considerable fibreglass work is required, but building one is still within the capabilities of most folks. Their low wetted surface area hulls move with minimal effort at low to medium speeds. These boats are best for paddlers who don't wish to camp or to paddle in rough conditions.