Built and test flew a friend's GP PT19 powered w/ an OS120 Surpass, which is a very good match IMO.

I think the plane has sufficient eing area to handle the G23's weight, though you might have to move the servos to the tail for balance.

Oh, by the way; we found the CG listed in the manual to be approx. 3/4" TOO FAR BACK, so beware!

It's great looking plane - perfect for a relaxing Sunday at the field.
Here it is in flight.