Sorry - Posting a link to that site is not allowed here. Need to respect this site owners wishes.
However its easy to find. Just go to the Main Grand Design Web Page and look under support for the technical forum. Then use the search feature.
There are also good tips over at IRV2. Also a few good U-Tube videos and not so good ones too
But to save you some time the trick I learned to keep the coroplast in place while you fasten up use a 2x4 full width and a second one running length wise in the center. You need to have the center snug up to get things on the edge to re-attach. Use clamps at the frame edge or jacks to hold the boards in place. I used wood working clamps. The trick is to work side to side as you move along the trailer. Sometimes a good set of vice grips help you pull the coroplast into position while it is held up by the boards. The coroplast was originally installed with the frame upside down.
Hope this helps.