Its supposed to be a small,
: maneuverable kayak for short day trips and twisty little rivers.

Well, it appears your design has little rocker. More rocker=more maneuverability.
If you don't want "full on greenland design" then consider vertical stern (longer waterline lenght,better speed, also easier wet entry from the back)
Also, it seems the max beam is almost the same as the max waterline beam. If you increase your max beam you will gain a bit more secondary stability without affecting other characteristics of your desing
-Just my 2 cents