My ramp is 28 inches long. That's 2 grids zip tied together. Grids are 9 squares across, so I bent the grids so there are 5 squares running down the middle and 2 on each side to make a railing. Mines wider then most, but if you want to take up less room you can make it smaller.
I wouldn't trust coroplast to be sturdy enough on it's own, but that's only my opinion. I used a piece of coro to line my grid ramp so piggy feet couldn't fall through the squares.
Check out the photo galleries. There's one specifically for ramp designs and building suggestions,
