The USB spec defines maximum plug sizes and minimum port spacings, different for all connector series (A/B/mini x/micro x). USB A plug/device dimensions are specified as 16x8mm MAX, i don't remember minimum spacing between A ports and google isn't cooperating, but it's also defined somewhere in there. There are some problems however:
If you don't want to put an USB logo on your device or otherwise use USB trademarks you don't need to follow the spec to the letter and USB IF can't do anything about it (see every other usb novelty device like lamps, fans etc).
If your device is too large you just need to ship it with an extension cable and it's ok.
If you don't want to put an USB logo on your device or otherwise use USB trademarks you don't need to follow the spec to the letter and USB IF can't do anything about it (see every other usb novelty device like lamps, fans etc).
If your device is too large you just need to ship it with an extension cable and it's ok.