those plans don't make a 4x2x2, they make a 4x2x1 and doesn't make a door, it makes a box, doesn;t take into account the thickness of the wood, don't use those plans.

but when you find a good set of plans, if its a 4x2x2, you just have to add 24 inches to every measurement for the length. if thye call for a 23.25inx46.5in, you make it 23.25inx70.5in. its pretty simple.

as far as a door, the plexi has to be small enough to fit in the opening of the wood. if its a true 2ftx6ft cage, the thickness of the wood makes the opening 22.5inx70.5in, then the track will take up a little more room. just gotta keep in mind what your doing to make sure it fits