Battlecruisers - Box Protection?

So, I read that the consensus was that box protection was a wasted effort; just go All-or-Nothing, or don't even bother armoring!

But... I was looking at making a BC with 10" armor belt anyway. Then I wondered, "can I make a 20" Box Magazine belt?

And I COULD! This is still 10" everywhere, but it's an extra 10" over the Big Boxes o' Boom in the middle of my ship. I was even able to get an extra .5 inch of deck armor. Yesss, that means that the rest of the ship is more vulnerable to plunging fire, but at 34 knots, good freaking luck hitting the sodding thing with plunging fire!

I'm not sure if this is a good idea or not. But I'm gonna try it!