Building a sump tank vs buying one!!!

[match55]

I m deciding which to do, the LFS sump tanks r expensive.
they r trying to get a quote from some company since the weird dimension I have for my sump. (custom build will probably more expensive, right?)

the dimension I have is L18 W16 H16~
anyone have suggestion for me??
like where to get acrylic and how thick the board should be?
the buffle size (H, and how far should it be?)

here is a top view sketch for my sump.


as suggested by other fellow members in my other thread, I will use eshopps 300 overflow, and probably via aqua 1800 as returen bump.

btw if anyone live close to pleasanton/dublin in bay area and know how to build one, I would love to meet with u and get some help from u. (I will pay if u want!)