Unless your really into scale flying you will not be happy with the Saito 180 on this airplane. You will be constantly flying it on the wing and will have to pay close attention to moves to make sure you don't stall the plane.

My CE, with 50cc weighed in at 18.5 lbs. It flew extermely well with the Bolley 20"x10" prop spinning close to and sometimes exceeding 7000 rpm. Your Saito will shave some weight but I don't know how much because the 5lb gasser left me with a CG that was spot-on with no extra weight. Your Saito will not give you that kind of performance.

I would opt for the 50cc gasser and leave the Saito for a 1/4 scale aerobat.