If you mount the bottle directly to the tunnel in between the rear seats will it be able to raise up high enough to make up for the downward slope of the tunnel, or will I need a more level surface? I couldn't find anything on this with the search but I remember seeing some pics of something like this.

A few people make this bracket, but here is the one from HSW.

http://www.harrisspeedworks.com/shop...cat=268&page=1

 

The HSW piece has alot of adjustability to it. I didn't even adjust mine all the way out and the slop is perfect.

 

Yeah you mounted it to a level surface. I was wanting to mount it to the tunnel itself. If I spend the $70 and get that tunnel mounting plate from nitrous outlet I'm just gonna use the brackets that came with my kit and save $150. The adjustable piece does look nice though.