If you are going to buy a new Malibu Kayak they now come with a transducer ready spot underneath the back of the kayak.
Here is the link for it:
http://www.bigwatersedge.com/bwevb/s...ibu+transducer
The only bad thing is that they do not fit the Lowerance HDS 5.
For the mount I would recommend a ram mount so you do not have a mount stick up 8 inches off your kayak.