The J/BB/1927 Design: a ship that finally has adequate protection

The size needed to balloon considerably, but the J/BB/1927 design finally has adequate protection against gunfire, unlike its predecessors. Having a 6in secondary battery is rather a retrograde move, but is historically accurate. The tertiary armament now has 5in DP guns in twin mounts. I am using the odd 57mm AA guns, which is not historically accurate. This is the Springsharp report:

J/BB/1927, Japan Battleship laid down 1927

Displacement:
 70,439 t light; 73,605 t standard; 78,500 t normal; 82,416 t full load

Dimensions: Length overall / water x beam x draught
 900.57 ft / 895.00 ft x 122.00 ft x 33.00 ft (normal load)
 274.49 m / 272.80 m x 37.19 m  x 10.06 m

Armament:
      10 - 18.00" / 457 mm guns (4 mounts), 2,916.00lbs / 1,322.68kg shells, 1927 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, evenly spread, 2 raised mounts - superfiring
      12 - 6.00" / 152 mm guns (4x3 guns), 108.00lbs / 48.99kg shells, 1927 Model
   Quick firing guns in turrets (on barbettes)
   on side, all amidships
      12 - 5.00" / 127 mm guns (6x2 guns), 62.50lbs / 28.35kg shells, 1927 Model
   Dual purpose guns in deck mounts with hoists
   on side, evenly spread, all raised mounts
      42 - 2.24" / 57.0 mm guns (21x2 guns), 5.65lbs / 2.56kg shells, 1927 Model
   Anti-aircraft guns in deck mounts 
   on side, evenly spread, 18 raised mounts
 Weight of broadside 31,443 lbs / 14,262 kg
 Shells per gun, main battery: 90

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 16.0" / 406 mm 640.00 ft / 195.07 m 9.00 ft / 2.74 m
 Ends: Unarmoured
 Upper: 12.0" / 305 mm 640.00 ft / 195.07 m 8.00 ft / 2.44 m
   Main Belt covers 110 % of normal length

   - Torpedo Bulkhead:
  5.00" / 127 mm 640.00 ft / 195.07 m 32.00 ft / 9.75 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 16.0" / 406 mm 12.0" / 305 mm  16.0" / 406 mm
 2nd: 6.00" / 152 mm 6.00" / 152 mm  6.00" / 152 mm

   - Armour deck: 7.00" / 178 mm, Conning tower: 16.00" / 406 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 232,185 shp / 173,210 Kw = 30.00 kts
 Range 10,000nm at 15.00 kts
 Bunker at max displacement = 8,811 tons

Complement:
 2,344 - 3,048

Cost:
 £24.702 million / $98.807 million

Distribution of weights at normal displacement:
 Armament: 3,930 tons, 5.0 %
 Armour: 30,600 tons, 39.0 %
    - Belts: 6,547 tons, 8.3 %
    - Torpedo bulkhead: 3,789 tons, 4.8 %
    - Armament: 7,661 tons, 9.8 %
    - Armour Deck: 11,971 tons, 15.2 %
    - Conning Tower: 632 tons, 0.8 %
 Machinery: 7,329 tons, 9.3 %
 Hull, fittings & equipment: 28,580 tons, 36.4 %
 Fuel, ammunition & stores: 8,061 tons, 10.3 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   115,996 lbs / 52,615 Kg = 39.8 x 18.0 " / 457 mm shells or 20.8 torpedoes
 Stability (Unstable if below 1.00): 1.11
 Metacentric height 8.3 ft / 2.5 m
 Roll period: 17.8 seconds
 Steadiness - As gun platform (Average = 50 %): 55 %
   - Recoil effect (Restricted arc if above 1.00): 0.71
 Seaboat quality  (Average = 1.00): 1.09

Hull form characteristics:
 Hull has a flush deck
 Block coefficient: 0.763
 Length to Beam Ratio: 7.34 : 1
 'Natural speed' for length: 29.92 kts
 Power going to wave formation at top speed: 53 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 6.00 degrees
 Stern overhang: 2.00 ft / 0.61 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  34.00 ft / 10.36 m
    - Forecastle (20 %): 27.00 ft / 8.23 m
    - Mid (67 %):  27.00 ft / 8.23 m
    - Quarterdeck (15 %): 27.00 ft / 8.23 m
    - Stern:  27.00 ft / 8.23 m
    - Average freeboard: 27.56 ft / 8.40 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 81.5 %
  - Above water (accommodation/working, high = better): 202.8 %
 Waterplane Area: 92,439 Square feet or 8,588 Square metres
 Displacement factor (Displacement / loading): 102 %
 Structure weight / hull surface area: 233 lbs/sq ft or 1,136 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.99
  - Longitudinal: 1.09
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is excellent
 Room for accommodation and workspaces is excellent