I got 10 pairs of Lontan soft close slides and got them all installed in the kitchen now. The boxes, made of 3/4 plywood, weigh 13 pounds! This was the widest cabinet yet, but also the most useful...I found that although you can see everything, and get to everything, you can't get quite as much stuff in the cabinets with the drawers compared to heaping it in with no drawers. This is more true on the narrower cabinets.
I presumed my factory cabinets were square, but that wasn't always true. Near the bottom, yes, but on this wide cabinet, near the top, not true. I used the brackets, so a simple matter of moving one side over to get the slides parallel.