Stablize is OK, Loiter with forward speed will have a severe vibration

ArduCopter Copter 3.5
1

We use copter 3.5.5 for our hexa-rotors UAV.
The Vibration is in good level in stabilize mode. but changed worse in Loiter mode with forward flight.
Can anyone help?
the bin file is as follow:
https://drive.google.com/open?id=1C6132u1E64skSc9PigH2fo_lYiGeA2xO
https://drive.google.com/open?id=1Ib5Hd0XNB1VGVziVhc8i_GbKc2HofaWr

2

Did you balanced props, checked bad bearings and loose components, cables onboard ?

3

Yes, we did, we also arranged the cable in C shape to avoid magnitude interference.
We didn’t use vibration isolation for autopilot. we tried damping materials, the vibration level was getting worse.

4

Are you the same guy on RCG with the hex that has the middle arms WAY longer than the other 4 arms?

5

Yes, the middle arms are longer than the other 4 arms.