Extreme Z-axis vibration after prop change


I post this in Copter/3.01 because I’m not sure if it’s a hardware or tuning problem.

I recently changed the power-train on my 70cm quad from 800kV with 10x4.5 props to 390kV with 15x5.5 props. I didn’t have time nor weather to re-tune yet but I did a few test flights and noticed that I have Z-axis vibrations between -5 and -15 with 10Ah bat and -3 and -16 with 5Ah bat. Before, my Z-axis vibes were around -8 and -12.

Now, what makes me suspicious is that X- and Y-axis vibes are between -2 and 2. That’s still worse than before but not as bad as the Z-axis vibes in relation.

Of course, I did balance the props. I also have now 3 stages of dampening. The APM is mounted on a base of anti-vibration foam. That foam is velcro’d to a plate which is connected to the electronics base-plate via 4 rubber balls. The electronic base-plate is mounted to the frame with 4 rubber anti-vibration mounts. Additionally, on the base-plate is a roof-plate mounted with nylon-standoffs and on the roof-plate sits a 3DR GPS/compass module, so the electronic base-plate does have some mass.

The copter is a bit overtuned at the moment. It bounces after sharp maneuvers and it’s overall a bit shaky, but not extremely.

Now the question: Is it possible that the vibrations are caused by mistuning/overtuning or are vibrations in any case hardware-caused?

The plot thickens. My copter draws (according to telemetry) about 22-26A in hover while it should only draw around 11 due to experiences of other users with a similar motor-setup.
I think, I remember that after tuning my last quad, the amp draw went down significantly.
Does that make sense?