OK so I have been in contact with several enclosure manufacturers and can not find an enclosure in the 1590B size range that is not tapered unless I go with extruded aluminum or plastic.
The manufacturers told me the reason for the taper is so they can get them out of the mold for the die-cast. Having done some metal work in the past it doesn't make much since to me considering the thermal expansion of the two metals are different the Die-cast should come out of the steel due to the aluminum having a higher thermal expansion. But I am not an engineer and I am sure there is a true reason for the taper.
The bad part about it is that I have built projects using the Hammond boxes long before I knew about any PVs other than the older Blu and I never noticed the taper away from the door side. Now I notice it with all of the boxes at the shops I frequent.
One upside to it starting to get noticed is I am being asked to make some new boxes for people. Most are finally seeing the light(safety) when it comes to using regulated boxes over these slap together (Custom) jobs that they have all spent money on.
If anyone has seen any of the boxes that do not have a taper and would like to share I am sure we would all be very appreciative of it. I know I would be.
One thing I have found is the 1455 Extruded Aluminum boxes from Hammond that are kind of nice. The only problem I see with them is to get a removable panel besides the top and bottom I have to go to a three inch wide box. and man are those things tall, almost 4.75 inches. The nice thing is they come in clear(natural), black, blue, and red anodized colors so they should be pretty durable. And the anodizing looks to be of good clarity and quality.
These boxes would be great options for some of the builds I have seen on the site. They are a bit more expensive than the usual Hammond boxes unfortunately.
They are also slotted on the inside to accept pcb boards.