I have this same plane. Maidened it a couple weeks ago. My initial balancing was right on to a tad tail heavy and this is not good. I stuffed my 1800mah battery up under the fuel tank and added a bit of weight. Those CG machines a nice but i do mine with my finger. I find the CG on the bottom of the plane. I put a little bit of pinstripe on the bottom on each side of the wing.
Then I get in front of the plane put my hands underneath and feel for the tape. Pick it up and it the nose drops. I am a happy man. If it balances perfectly, well I add some weight. I feel its better to have the plane noe heavy than to be right on. My best guess is you flew a tail heavy plane.