Hey Guy,
To find the throttle curve settings, go to Parameters and wait until they all download (the green bar goes across near the top). In the Search box type in H_ (with underscore) and you will then see all the H_ parameters for heli.
It sounds like you might have too much negative pitch set up. Or you do not have the H_COL_MIN, H_COL_MID and H_COL_MAX set right.
There is a setting you will see, H_SV_MAN. Set that to Mid Collective and your blades should be at zero pitch. If they are not, set the H_COL_MID so they are at zero.
Now set H_SV_MAN to Minimum Collective. Your blades should be at -2.5 degrees for the GX9. It is too heavy of a heli for 3D aerobatics, so you only want -2.5 for autorotation in the event the rotor stalls. If it is not at -2.5 deg, then set H_COL_MIN so it is.
Now set H_SV_MAN to Max Collective. Your blades should be at 11 deg. If they are not, set H_COL_MAX so they are.
Now set H_SV_MAN back to 0 or disabled. And set the IM_STAB_COL’s back to 0, 400, 600, 1000. Move the collective stick and you should get smooth operation of the collective from -2.5 to 11 degrees as you move the stick. Note you cannot use any sort of mixes in the radio. If you use a mix in the radio it won’t work. So with most radios using heli mode in the radio will not work unless you select H1 swash type (straight swash) in your RC radio menu. Best, if you are not familiar with how to set H1 swash type in your RC is to just use airplane mode in the radio, which does not have any mixes.
In QGroundControl in the Parameters button, you will see a button that says Tools on the top right. Click on it and you will get an option to export your parameter file. It is saved by default in your QGroundControl folder in your computer or tablet, in the Parameters folder.