Keep in mind that a sign cabinet with faces this large will not be easy to service. I have serviced signs that size, and larger, that were almost impossible to open up. I occasionally resorted to putting a clamp on an edge of the face so I could tie it off to my bucket lift and use the rotation function to slide the face sideways. Then I would slide it back from the other side using the same method. And at some point in my career, I vowed never to build a cabinet with a large face that did not have hanging bars. I have never been a fan of large one-piece faces. One shop I worked at for a year or so back in the '80s had a standing rule that long faces would always be made in two pieces with a field seam. That way the sign could be safely serviced by one worker and one truck. A second truck doubles the cost of a service call. In a union shop back in the 70s, that meant 200 dollars an hour instead of 100.
Another issue with a big face, perhaps the main issue, is the chance for a blowout. A hanging bar, of course, is good for preventing this. I have seen some fabricators, on occasion, put a bar at both top and bottom. And one clever guy used to make a hanging bar with wheels, somewhat similar to the kind closet doors ride on. I believe he inset a ledge at the top of the cabinet for the wheels to ride on. That meant the bar was attached to the
back of the face instead of the front, and the weight of the face was supported by the top of the cabinet rather than the top retainer. This was back when everybody built lighted signs from angle iron and a skin made of aluminum or Paint-Lok steel. A good sheet metal worker was a valued employee back then. Now, everything is mostly mitered extrusions. Even I can put them together.
An acrylic pan face resists blow out better than a flat face due to the stiffer edges. It's easier to slide, too.
Of course, the best (and most expensive) way to replace a large face is to install a flexible face using a retrofit frame kit. While a typical extruded aluminum cabinet may not have the strength to hold the tension of a flexible face, the retrofit frame kits are designed to do so. With the top of the face hinged to the old cabinet, a sign can be serviced quickly and easily. Even by me.
Brad in Kansas City