With no other changes... more weight in the nse makes the airplane dive.

So to take off... you put in more up elevator.

Fill the tank and take off.

Trim for level flight just a bit above stall speed, and add power, the nose will rise.

Leave the trims alone and land. Drain 13 oz from that 17 oz tank (should still have over 3 oz... just one pass around the field won't burn much. Or drain it competely and put 3 to 4 oz in.)

Take off again... you won't need to touch the elevator... the plane will rotate on its own at just a bit above the previous level cruise throttle setting.

Don't touch the trim!

The plane will constantly need down elevator to stay level even with a slightly lower power setting. It may even want to stall all the time rather than being able to have the power set easilly for level flight.

Try a MORE power and let it settle into a stable climb, then slowly reduce power until it no longer gains altitude. (still don't touch the trim...) THAT will work. (This is flying on the "backside of the power curve" See the book I referenced.)

Pulling up (if on the backside of the power curve) will make the plane MUSH and lose altitude.... it WILL NOT CLIMB with up-elevator! PUSH a little down elevator and watch it ZOOM up!

THAT is flying the wing... rather than pointing the prop.

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Demonstrate that at the local field... the trick of climbing with down elevator will AMAZE 80% or more of the pilots.