I would, but both of my cars are Infiniti.
Same issue on the EX35. I can tap the ground cable to the frame, and I can get the light to flash, but the power is immediately cut. Not sure if it is happening on the Infiniti side or from the Blackvue. Blackvue has been ZERO help on the matter. Tried to Power Magic Pro's and had the same issue with both. Ended up just pulling the device.
The funny thing, my PASSPORT radar detector is wired in and works fine. Using ACC Outlet fuse and ground under the dash without issue. Both Blackvue Power Magic Pro's won't turn on or keep power.