I built a GA for my daughter. It doesn't have a skeg (although I may
decide to add one sometime) and it tracks very well for me, and seemed to
do just fine for Heather (a friend's daughter) when she paddled it on the Conwy ascent (this is an upstream paddle on a spring tide). However, the
boat is built 5/6 of the design size - that is about right for Heather and
Sarah, but the boat is very overloaded when I paddle her, which means she sits
lower in the water than a full-sized one would. If the water is flat enough
that I feel comfortable leaning the boat over, the secondary stability is
more reassuring than you expect for a short, overloaded 20 inch beam boat,
and she turns very well.

Andy