That's opening a can of worms that I've never once seen end well in all my years in RP. I'd make a sweeping generalization like "nothing except hyperdreads can be significantly larger than 6000 meters" and leave it at that.

[b]EDIT:[/b] To better clarify my thoughts: design doctrines are going to be wildly different across military forces. On one hand, you're liable to create hurt feelings if someone ends up getting caught on the wrong side of arbitrary thresholds. On another, by creating upper bounds, you're inevitably going to have minmaxers going right up to the line to maximize their power.