Several guys in my club have flown Phaeton 90's on G23 power with great sucess. I had one that I flew for about 8 years until a broken elevator clevis did it in. If you build a Phaeton 90, I suggest that you put about 1 to 1.5 degrees positive incidence in the stabilizer. Makes it much more pitch stable when changing throttle settings.
Several were built with additional small ailerons in the top wing. Greatly improves the roll rate.
A 16-8 APC prop is a great prop for the G23.
Enjoy!