Good luck with your rubbermaid sump. I tried that whole thing and ended up making one out of a 55long AGA. You may be able to research some of Squidd's threads, I know he has used homemade rubbermaid sumps before. I coudn't get my skimmer to sit level in a rubbermaid, which will affect the skimmer performance.
IMO, a 30g sump is too small for a 150DT anyway.