Sketchup does NOT design boxes, nor has it ever, nor will it ever. I don't care if it looks cool or whatever else you might think when using it: you're not designing an enclosure. Sketchup is a very useful, but completely unnecessary aid to enclosure design. It's used to visualize and nothing more. If you don't already have an enclosure design before making it into 3D, stop, pick up a book and learn what you're doing so you don't keep flooding the forum with "problems with my box, does this design look better" because you didn't actually design anything.
That's all, hopefully someone will realize that their enclosure was tuned to ~80hz not because sketchup wasn't good, but because they had no clue what they were doing.