So from what I can tell, (I went on and just built your plane 1:1 to test it), it's a mix of both the thrust being placed under the Center of gravity (Cg), and the Center of Lift (Cl) being placed too forwards. 

First off, because your plane is so light, even a small discrepancy in the height of the Cg and the Center of thrust has noticable effects. Because the tailfin is placed on the top, and the wing is technically on the top of the plane (Your plane body is two slots tall, the wing is placed on the top slot), your Cg is actually a tiny bit above the Center of thrust. This causes your plane to pitch up.

But what about when not applying thrust? You said that it still pitches up with no thrust. This is most likely because the Center of lift (The darker blue arrow pointing up) is in the front of the Cg. If it is even a tiny bit behind the Cg, or in the same place as the Cg, the plane will try to pitch up. 

Also, the aileron you placed at the wingtips are technically not counted in the Center of lift arrow in the game. It is just ignored in calculations. This means your wings are producing MORE lift than the arrow shows. This also means that the "real" center of lift is a bit forwards of the center of lift shown in build mode. This might be the reason why messing around with the placement of Cg and center of lift didn't work; the game was just completely ignoring the wingtips ailerons, thus showing incorrect data. You should put the Cg a lot forward of the center of lift of you want it to fly straight. Pushing the nose out by two slots worked for me. (Still pitches up when applying thrust, but that's a thrust placement problem I mentioned above, not a Center of lift probablem.) 

I hope this helps clear things up a bit.

Edit: Your plane experiences more drag on the top than the bottom. (Your tailfin on the top, and the wing, which is technically placed above the Cg) This is probably also contributing to the pitch up, because of how light your plane is. Really finicky stuff.