C&C Chloroplast for 2x5 C and C cage

Your grids measurement is off. A 2x5 would be 28" wide by 70" long. (2x14=28 and 5x14=70) A 2x4 is 56" long.

For the sides, just add how tall you want them to be to the length and width (on each side).

Say you want the standard 6" sides all around, except for the back, which you want to be 12."

You would add 6"+12" to the 28" width, getting a total of 46" wide

Then you would add 6"+6" to the 70" length, getting a total of 82" long

So you need a piece that is at least 82" long by 46" wide