I have a 100G rubbermaid sump that I need to add at least one baffle to it and I need a couple of ideas. I was thinking of using star board b/c its easy to cut, but I can't find it anywhere. They have it at home depot but its real thin and I would like a thicker piece. If anyone knows where I can buy this at or near Flint/Grand Blanc that would be great. Once I find it what is the nest way to seal it? Some type of pond foam? I'm sure I wont be able to cut it to the exact size.

Then I need to get the water out and into something else long enough to do this

Any pointers will help.

Thanks