RE: Dx6i
your pitch curve should start at around 30 in normal mode or you'll have full negative pitch at 0 throttle, this makes the hovering stick position much higher than it should be. you should have about -2 pitch at 0 throttle so play with the pitch curve until you get that.
here is a fairly basic set up for the head.
The first thing you have to do is set up the head correctly. Pick a new model and name it then in the menu go to advanced menu. Set up the idle up curves first.
for idle up 1 set up the throttle curve to 100-75-50-75-100 and the pitch curve to 0-25-50-100.
then with the transmitter on, unplug the motor from the esc and then plug the battery in. once it all initializes put turn on idle up 1 and put the throttle stick at the mid position and check to make sure the servo arms are at 90 degrees, if they aren't then unscrew the servo arms and put them back on as close as possible to 90. once you have them close then use the sub trims to get them exactly at 90 deg.
once you've done the servos put the rods from the servos to the swashplate on and check the swash level. do this while you're still in idle up at mid stick. you should try to get the swash level when the mixing arms are 90 to the shaft. if you have a leveling tool (most of the ones from a 450 size will work as they have the same shaft diameter) use that. if not then do it by eye. once you have the swash level check the pitch on the blades. they should be at 0 deg of pitch. if you aren't then change the link lengths from the servos to the swashplate to get the pitch to 0. once the pitch is at 0 everything should be level at 90 degs. the servo arms, mixing arms and flybar arms should all be 90 deg to the main shaft.
once you have the swash level at mid stick move the throttle stick to the top and bottom and make sure the swashplate is still level, if it isn't level at the top or bottom use the end points in the radio to make the swash level. at this point the swashplate should be level at bottom, mid and top stick.
this process is not fast and make sure it's done correctly. Once this is done you can set the normal mode curves. throttle will be 0-40-60-80-100 but the pitch curve may be different. I'd try the pitch curve at 30-53-76-100, check the pitch of the blades at the bottom and top stick, they should be -2 and +7 or so.
let me know if you have any questions.