I used bolt to hold the bottle brackets in the trunk. I had to drill 4 holes in the trunk. I be legal at the track, you are not allowed to run the nitrous line inside the car. So you should drill anothe rhole in the trunk and run it under the car.
However, I have had my NOS line inside the car (under teh carpet) for 4 years and have never been questioned.
i have to nitruos bottle in my trunk and i run the hose under the car without drilling. look under the carpet u will find 2 holes, one on each side. they are in the in the front a little pit and covered with rubber cover. take the rubber of and run the hose throu there.
Like stated above...to be "track legal" it should be outside the car but if you're just running test and tune most tracks to 'tech' the inside of you car. I mounted my bottle to the spare tire cover in my trunk so i can take everything out of their when i need too. Its not the most "secure" mounting in the world as far as flopping around goes but with the spare under it, it supports the weight and my single 10" sub keeps the board down pretty good. I plan on changing it when I drop my tank though with bolts through the floor.