First of all, sorry for the language but my german is mostly some Rammstein lyrics.
But as your forum was great help installing dashcam to my #5 Brabus, I thought to share few installation pictures. Installation was easier as I thought, it's mostly just tucking the cables between chassis and interior. Hardest part was to find fuse box! Anyway, it took me only 1 evening to install and I'm not a professional but installation looks good atleast in my opinion.
Only panels / covers I needed to remove were fuse box cover, A-pillar cover (no need to remove completely) and trunk center cover. And yes, I have 4 cameras but only 3 channels on Viofo 329s because I couldn't decide do I want telephoto or interior camera. But as you can see from the pictures, it's 10s job to switch the cable from interior to telephoto camera. I guess I'd need to switch camera firmware also when doing this, but atleast I got good image from telephoto camera too with interior camera firmware.
And about the cables, Viofo 329s standard cable set was mostly enough. Just used shorter 0,5m cable for cabin/telephoto camera as it came with 1m cable.
Summary:
Viofo 329S
Interior+telephoto camera with 0,5m cable
Rear camera 6m cable
Viofo HK6 hardware kit comes with 3m cable and this was Just the right length.