I say 9 because the items you have equipped need to be unequipped in order to move, hence they simply replace whatever from the 9 open slots you've replaced them with. Patches/re-balancing doesn't happen often, and it will NEVER happen for older gear or weapons. You're more than free to play how you want, but Bungie doesn't need to cater to people who're holding on to obsolete items for their sentimental value or hopes for a buff that will never happen.