OK, so I decided to build a planer sled. Just a simple one mind you, it just ain't working!!!

So, I took a melamine shelf and glued-and-screwed to it a 3/4" piece of MDF. It was resting on a flat surface, and I weighted it down with bricks to dry. Took the bricks off, looked great, set it in the shop for a few days, and BINGO!! The whole thing bowed in the middle. AAARGH!!

Back to square one. I know there are numerous threads on here with many options, but I need something that has really been tried and tested. So, as I need to build another one, any suggestions from real world experiences, and not was just in some article.

Oh, I will build it a little over 6' long, so weight is an issue. The one I built was the max weight I want.

Thanks!!