The H45 was (sadly) not a realistic design to begin with...the blast force of a 31.5-inch gun would be incredibly powerful, and no human could feasibly stand on the deck of a warship when something like that was firing. The IJN's Yamato-class BBs had mere 18.1-inch guns (I used the word 'mere' because let's face it...compared to H45, the Yamato's a destroyer) and the blast pressure from those guns were so great that a normal human would be knocked flat, lose consciousness, and have the clothing blown off his body. The blast pressure from H45's guns would leave a human nothing more than a bloody smear on the side of the superstructure or a pile of lumpy red goo on the deck.
I'm just going to repost this because it bears repeating:
Just something that came up on another board recently:
It's much, much better than that. Over on the Warships Project Board, the idea of an eight-Dora battleship came up and somebody worked out a rough "design" to show what would be involved in such a ship. The resulting design came out as a 700,000 tonner that the poster jokingly called the H-45. Then, a wunderwaffe author called David Porter came along, saw it and decided it was just what he needed to complete his latest book about Nazi superweapons and included it as a genuine project. Then, somebody took the information from that book and used it for a Wikipedia article. Despite people telling said person that the data was false and showing where it came from, the idiot kept re-inserting it on the grounds that nobody could prove it didn't exist.
Wee for the Wunderwaffe!