Maybe it is your controller that is causing this? Using my MS Sidewinder FF 2 joystick, I have to pull back to takeoff. If I don't, I will be going faster than the V² bug before taking off. And so you know, I do not push forward to keep the nose on the ground for longer, I keep the joystick centred until I pull back on it.

Maybe it is because you have too much weight towards the back of the aircraft with your payloads and this causes the nose to rise earlier.

Mark