I don't know what kind of flying you do. But the Saito 1.25 on this plane is a good sport flyer. Vertical will not be unlimited by any means. That being said, as long as you don't care if it hovers or 3Ds the 1.25 is a good choice. It will get better with time. I would leave the 16x6 for now.
Curious, why do you think it needs more right thrust? Also, have you checked to see if everything else is straight? When I assembled mine I had a hard time getting the top wing mount straight. Lay a yard stick from it to the rudder post and see if it's dead on. I spent a lot of time getting mine right.

David