Recent experience with Serpac:
I began designing a product with a Serpac enclosure and quoted the part and cutout modifications. After about a month I finally received a prototype from them, having already finished the design of my PCB.
Well, it turns out the top and bottom were thicker than the drawing (including tolerances) by over 1.6x. This meant the interior height was reduced by 10% over the specified minimum. As a result, I could no longer fit my product inside.
Serpac admitted that it was a new product and that they screwed up the mold, but were unwilling to fix it or work with me in any way. Well, they suggested I pay them *more* money to have them machine to the proper height to fix *their* mistake.
I will not be making the mistake of designing into a Serpac enclosure again.