You're right, Dave! It is a monster motor! I'm sure the motor has plenty of power. I was just thinking that the "wibbly-wobbly" action came because I backed off the throttle so that the plane would slow down a bit. I like to fly slow. However, like I mentioned, the plane turned out heavier than I had anticipated so perhaps this plane "needs" to maintain a certain amount of speed for a successful flight.
I will try again today and I will try to remember to maintain some speed and we'll see what happens.