I mounted an elite 4 on my Revo11 recently: fantastic unit, I can only imagine the Elite5 would be that much better.
Looking at the layout of your quest...
The spot you mentioned sounds good.
You will need this mount: http://store.navico.com/Products/000-10909-001
it comes with the RAM ball so you could then get the rod holder attachment later on.
From my short experience thus far here are some helpful tips:
1. My elite4 has two ports on the back, one for power/transducer and one for optional accessories. I went to sea and got soaked, and the port that was left open got green with corrosion on the same day, dont let this happen to you. Cap the unused port
with tape or a rubber cap like they sell for automotive vacuum ports.
2. Spend the time to drill and route the connections through the hull by the RAM mount, and seal the area with silicone. I tried to be lazy and run the cables through my front hatch and I took on water in the surf launch.
3. Installation of the transducer is a snap. I mounted mine to the inside of the hull just ahead of the round hatch between the legs. I used plumber's putty to secure it there and didnt have any problems with the accuracy of the readings (except for water temperature).
Good luck and post pics when you finish!