Yes I think it will make a difference if the rear wing gives enough downforce.I can definately vouch for the fact my tyres are wearing better with this set-up.
The metal tube aligns the mount in the centre of the car.
NO you dont need it...something like a stand-off from an old computer would do the job .
The stock upper arms in the v-one-s DONT have turnbuckles they are just screws ..there fore you would have to pop the arm off everytime you wanted to adjust your rear camber. I would recommend buying turnbuckles just from a convenience point of view however you dont NEED to if you dont want to.
V-one s My prices were a pretty good guess hey!