[KC, Marc here is the resident acrylic guru. He can make anything out of acrylic. I think he's about to go into the "biz" on us here. You should see the sump he made posted in one of the other threads. I'm thinking about enlisting his help to make a giant fuge so that I can use my sump as a skimmer compartment.
You know, unless you have other reasons for dong so, you really don't have to make this two seperate boxes, you can make it one box with a dividing sheet in between to keep the sand away from your skimemr & pump. Then drill a flow hole at the top of the divider. Or make it three compartments. Fuge, skimmer, & pump.
Second suggestion is, glue on a little strip or something to keep that urchin standing upright. It is a very tall, thin skimmer and it doesn't have the hang-on lip like the remora to keep it in place. It'll be like a pencil standing on end without some support.]