After paddling a Night Heron Single for about 5 years and a Night Heron Double for a year, I plucked up the courage to build a kayak of my own design.
The Night Herons are great craft, but like almost everything available with the exception of children's kayaks, they are designed for 75 kg (165 lb) paddlers.
Although I have never got around to testing the theory, I am fairly sure that the fact that I weigh 62 kg means that the NH sits higher in the water than it was designed to do and so is more affected by crosswinds than it would be if I weighed 75 kg. I just never got around to trying it out with 10 or 20 kg of ballast.
My wife wanted a kayak and since she weighs just a few kilos less than me, I used Ross Leidy's excellent Kayak Foundry to design a kayak for a 60 kg (130 lb) paddler.
It didn't need to be used offshore or paddled by 180 lb paddlers, so I had the luxury of not needing to make some of the usual compromises in the design.
My wife specifically asked for strong tracking, so I had a little rocker at the bow and a negligible amount at the stern.
She wanted it light and stable, so I made it 15 ft long, 22 in wide and used Paulownia for the hull and half the deck. The rest is WRC. It has one layer of 4 oz glass inside and out. I also kept the deck fairly low and had a bit less turn up at the ends than some designs to reduce the effect of crosswinds.
The result is everything I had hoped for.
It weighs just over 11.5 kg (25 lb), tracks beautifully and is just about the best beginners kayak I have come across. Of course it is a bit slow to turn unless you are prepared to lean (or edge or whatever the technical term is), but that is not a problem for the situations in which it will be used.
It is as close as possible to neutral in even very strong crosswind with no noticeable weathercocking or whatever the opposite of that is.
At the speeds at which it will be paddled, it is probably has less drag than an 18 ft kayak. Most of the graphs and tables I could find suggested that the crossover point is up around 4.5 knots.
It seems that if you don't need to allow for different sized paddlers or different applications as commercial builders and designers do, it is possible to produce a kayak that does exactly what you want it to do and better than even the well designed ones on the market.