Custom Tank Plan...help??

looks pretty good. i'd just suggest dropping the sump intake to the far side of the sump. force the water to travel the length of the sump (e.g. baffles, equipment space, water scrubber-methods, etc.). detail stuff: i'd add in disconnects/ball valves to each pump. it'll allow you maintenance and replacement ability when the pumps eventually burn-out without having catastrophic stress.

I've also read a lot about using a loop for your returns. Specifially, for your yellow CL returns, rather than T them off make a rectangular loop that feeds the them. Understand what I mean? If not, pm me.