User blog comment:WolfgangBSC/Wolfgang's Random Chat Room/@comment-24903406-20141112190539/@comment-11135771-20141112194758

IIRC the reason 10.5s were not banned on super warships and flying ships was twofold. First, flying ships and super warships are subject to the phantom glitch, which basically means that you can't edit them at all and thus the only way to ban 10.5s on those would be to ban every Hansa flying ship and super warship made up until that point, since they couldn't be retrofitted like the normal ships could. Alternatively you could just say that any ships created in future wouldn't be allowed to have them, but then that makes the old ones drastically more powerful than anything that can be created in future. Second, most Hansa flying ships and super warships will kill a standard size surface ship virtually instantly with their other weaponry anyway, so it doesn't matter too much.

P.S. Although there isn't really any rule about it, it seems to be generally agreed upon that 10.5s in RP are not nearly as powerful as in game. The ban on them was purely intended to make GC battles not end in three seconds, not to affect the RP in any way.