One problem is your prop of choice. A 14x6 turning around 10k rpm isn't healthy for the engine. You want it to turn at about 9.5k, which means you'd wanna go up a size. Remember that props unload a lot in the air. Go to a 15x4W for a couple gallons, then up to a 16x4W. Great 3D props, great thrust, great options. That's what I did, that's what worked.

I also agree with flygilmore, I've never heard of anyone trash-talking a Saito 100 AND recommending a heavier, less powerful engine instead. I've heard of cases where planes need the extra weight in the nose.