swashplate tool
Swashplate Leveler Tool for the HK450 Helicopter
I use the 450 Swashplate Leveler Tool for leveling my swashplate linkages to the servos

Why?
This allows you to see that your swashplate is level throughout the entire range of pitch, from full negative to full positive you can adjust the endpoints on your transmitter to ensure that the travel is equal across the travel.
Once you have a level travelling swashplate you are able to then setup the rest of the head correctly.
Regards
Elias Gourvelos (EatAtJoes)