I have sailed on "mid ships bridge" and "everything aft and I don't think there is more than cheaper to build and possibly less weight in "everything aft"

@ Bob Scott: ore carriers like sisters

RIO GRANDE: http://www.shipspotting.com/gallery/photo.php?lid=2451786
RIO MACAREO: http://www.shipspotting.com/gallery/photo.php?lid=2451790

Some more work needed for corrections then...

This was an ore carrier, not a bulker. See sister vesel RIO CARONI

The wheel has turned full circle... from sailing ships navigated and sailed from aft to early steamers with a 'bridge' amidships over the top of the boiler so they could see where they were going... to bridge aft .. and now back to bridge amidships on today's very large container ships..... so they can see where they are going.....
Bridges stayed amidships on ships like the one shown because the commonly held view was that such large ships could not be conned from 'down the back'.
That changed on tankers in the late 50's and onwards due to a number of bad outcomes for people living amidships when tankers caught fire and exploded.....

Would be a logical explanation, Denis, but rules must have been changed when the majority of new ships with bridge aft appear in 1960s.
Best wishes, Manfred

Maybe bridge amidships was used to have the required line of sight angle, which would be difficult due to length & high bow if bridge was on the aft?