most yaks can be handled solo w/o much effort. I have a Wilderness Systems Pungo 120 (my 1st yak as well) and I feel it is very stable, both stationary and when moving. I can wiggle in the seat, the yak moves with me but I feel like I would really have to try to flip it over. I have not cast from mine yet, I am at the bottom of the learning curve on fishing from yaks, I have done the dock shooting method so far, and it did not affect the stability of my yak.
GO BIG ORANGE !
I meant to behave, but there were just way too many other options available at the time.