APC 12.25-3.75 spinning at 13500 rpm is good and will produce about 4 kilos of thrust. This should be enough to lift your plane vertical out of a hover. If your plane isn`t able to hover then it is because of wrong balance or set up. Did you weigh the plane yet??

I had no problems going straight up with my Katana profile weighing 2.3 kilos and only powered by a 61 Fs (it was slow, but still)