Generally speaking,silicon doesn't bond well to plastics long term.If you scuff up the edges of the acrylic with sandpaper it'll work better.Since baffles usually don't have a big load to support its not a big deal anyways.I use 1/8" glass baffles in my sump because thats what Home Depot had.If i was to go to a glass shop,I'd probably just go ahead and use 1/4".