If you have a gallon of fuel thru the 100 it is more than enough time to adjust the low end needle, I adjusted mine some after about 4 tanks and check the valves also. After 40 minutes it should be broken in like the manual states, figure 10 minutes a tank and a gallon is at least 4 tanks, many more actually.
If you kill the throttle and the plane balloons up you need to add some upthrust to the engine, I had to do that on the electric version as my mount had too much downthrust in it. Too much downthrust will also make it pull more to the wheels in knife edge.
If you have too much downthrust in it flying at full throttle will require some "up" elevator trim to fly level, when you kill the power the elevator trim makes it balloon up.

I flew mine electric and then put a Saito 100 in it as I am writing a double review for Rcgroups and I did the electric first and am now doing the glow one.