RE: Bi-plane as second plane?
I have the GP Ultimate Bipe 40. I've been flying for 7 years. It is my 5th airplane. It is a very nice flyer and I highly recommend it, but not as a second airplane - maybe a third. I agree with the previous recommendations.... a 4-star or Tiger 2 make great second planes.
Biplanes do present a more confusing image in the sky. It is easier to get disoriented. With the GP Ultimate 40 you need to be aware of airspeed and manage the throttle on approach and landing.