Moving from 3.3.3 to 3.4.5

I have a hexa that i have fly perfectly for a year with 3.3.3 but know i m modified it to a coaxial X8 and i install the firmware 3.4.5
Is there something that is a very big change in the 3.4.5 and i have to look or just the usual calibrations are enough?

You should be fine. Redoing calibration is a good thing given you are changing (at least to some degree) your set-up/frame. See: Copter-3.4 has been released!

See also release notes, always good to check: https://github.com/ArduPilot/ardupilot/blob/master/ArduCopter/ReleaseNotes.txt

I want to Thank you OlivierĪ’