If it works for you good job.
A pair of 3" cylinders has a little more force than a single 5", but less than a single 4-1/2"
No, at the same pressure, a 5" cylinder has almost 39% more force than two 3" cylinders. the force is proportional to the square of the radius of a cylinder.
(Not to mention, how could two 3" cylinders have MORE than a 5" cylinder, but LESS than a 4.5"?)
Yea it's just over 15 tons but the two 3" cylinders had been taking up space in my shed for about ten years. Just wanted to use em for something.