Monitor Arm for 4th Display

[Hellish1]

I am looking for a single monitor mount for a 4th monitor to go over my current 3, I would like to be able to move the monitor either directly above the middle monitor (Center of monitors line up) or above a side monitor (side is irrelevant but it will be the left side). I can use either a desk mount or a wall mount. The wall mount will need quite a long reach (aprox 34" away from the wall is where the center of the mounting piece must reach). The desk stand must be able to hold a 27" monitor above the height of a 24" monitor.

I am looking for any recommendations, no custom work.

I have found one but not sure if it has the height and range I need http://www.newegg.ca/Product/Product.aspx?Item=N82E16882183897CVF

The current 3 monitors are all BenQ XL2420T, and the monitor I would like to purchase for the accessory display is the Dell S2740L.

 

[BecauseScience]

I have found one but not sure if it has the height and range I need http://www.newegg.ca/Product/Product.aspx?Item=N82E16882183897CVF

You can download technical drawings from the Ergotron site. They have measurements for all of the joints so you can easily figure out if the arm can get your display where you want it. That's what I did before buying.

 

[Hellish1]

The measurements are kind of weird, it does not tell me the max height the mount will be at, I essentially need the vesa mount part to be a minimum of 26" above the desk height. I simply cant just add the pole height as it doesnt list the height each arm raises and it shows the farther arm to have a lift of 13" but that is going lower then the pole not from the top of the pole yet the dual stacking one has a shorter pole but it able to put 2 monitors on top of each other, and in order to mount 2x 24" monitor on top of each you would need the center of the top mount to be about 23.5-24.5" off the table, yet if you add half of the lift height (6.5") as the lifts center is at about the top of the pole to the pole height you are only getting 19.2 on the dual arm, the single arm is slightly taller.