I tried and came away with these extra lessons after following those instructions;
First of all, measure your sump very carefully, not all tanks, even from the same manufacturer and the same size are equal, they can vary small amounts and those small amounts are extremely important with pressure baffles.
Make the cuts the tank width - 1/8 inch not 1/4, when I did 1/4 it wasn't even close to being enough pressure.
Use bracing like the guy above with PVC, personally I used egg crate positioned between every baffle front and back.
If for some reason you're against bracing don't even bother if you're going to have significant differences in water height between baffles, for instance if you're using a taler tank like a 55 gallon tank and your refugium is going to be 19 inches deep and the return section right next to it as low as 5 inches, the water pressure difference will be too much.
I'm using it right now in my sump and it's working okay, though I'd be lieing if I said I wasn't nervous about what would happen if some egg crate came out of place. My design got kind of screwed up though, I had my baffles cut perfectly and tested for the 30 gallon long tank I was planning on using, then a mishap occured in the middle of moving my tank from 1 room to another and my sump got cracked on 1 side. Luckily I was able to find a store in town with another of the samee size, unfortunately as I later discovered after a lot of frustration all 30 gallon tanks aren't created equally, the new one was about 1/10 to 1/8 inch wider than the one that cracked despite both being Aqueaon tanks, I still got it to work mostly but I had to use the egg crate, which is probably a good idea anyways.