The best place I found to mount the front cam on my XC, is beside the Headlights. At that position, there will only be a small part of the top fender within the picture. On a XR, which does not have the top fender, the best place would be under the headlights.
Mounting the rear cam is a little bit tricky, if you don't want to drill a hole (what I don't want). So I mounted the cam above the left indicator, using one of the four screws which holds the rack. Unfortunately you can't use the provided bracket, as it is a little bit too short. I bought one at a hardware store and trimmed it to fit.
For the DVR, there is enought space under the rear seat. I also put the power converter there.
Finding switch power
On older Tiger 800, you will find switched power at the horn. Just disconnect both cables and measure the voltage against the frame to find the correct cable.
On newer Tiger 800 (the one with TFT cockpit), there are two connectors where you can get switched power.
1) The white connector in the picture above. There are five pins in it.
xxx GND xxx
2) The connector which powers the USB port in the back (2 pins). You will have to remove the rack to get access to it.
If you want to buy a plug to make a proper connection...the manufacturer of the plugs is Sumitomo. I bought mine here