Hello, I put mine in the boot,out of the way. The best point for me was I could run a 20l tank (75meth 25water) and do a good 1 to 2 full tanks of petrol before I needed to think of refilling the system.
I`ve got a post in the gallery section
http://www.aquamist.co.uk/phpBB2/viewtopic.php?t=1442 , running a Shurflow with 6mm line to the front of the car. I`ll have to put some pictures up of the pump mounting.
I also have a VW Golf with an Erl pump in the rear and a 5l tank, works well.