My first experience in my Guillemot concerned me as well. It seemed to want to go anyway but straight. My 1st thought was that I screwed up in the building process.

Now, after much time in the boat, adjusting and re-adjusting the seat, and generally getting use to the handling, I realize it was me not the kayak that was to blame.

Other factors to consider are wind and current. Even light winds or currents can change the direction of your kayak. Being inexperienced I thought it had to be "blow your hat off" type winds to cause problems due to the low profile and lenght of the boat.

I would put in numerous hours on different types of water and under varying conditions b4 changing anything.

Whatever you do, have fun with it. Not much else feels like paddling a boat you built yourself.