The J/BB/1918 design (REVISED)

For the J/BB/1918 design, I escalated the basic design with another twin 16in gun turret and a knot more speed. There is a more effective AA armament and a 4in armoured deck. The roll period is now 17.5 seconds, which is abnormally long. The belt is now 12in, as well. There seems to be still an inadequate defence against gunfire, if the ship will only withstand 28.2 16in hits. This is the Springsharp report:

J/BB/1918, Japan Battleship laid down 1918

Displacement:
 38,312 t light; 40,322 t standard; 44,100 t normal; 47,122 t full load

Dimensions: Length overall / water x beam x draught
 766.96 ft / 765.00 ft x 104.00 ft x 31.00 ft (normal load)
 233.77 m / 233.17 m x 31.70 m  x 9.45 m

Armament:
      10 - 16.00" / 406 mm guns (5x2 guns), 2,048.00lbs / 928.96kg shells, 1918 Model
   Breech loading guns in turrets (on barbettes)
   on centreline ends, majority forward, 2 raised mounts - superfiring
      16 - 5.50" / 140 mm guns in single mounts, 83.19lbs / 37.73kg shells, 1918 Model
   Quick firing guns in casemate mounts 
   on side, all amidships, 8 raised mounts - superfiring
      6 - 4.70" / 119 mm guns in single mounts, 51.91lbs / 23.55kg shells, 1918 Model
   Anti-aircraft guns in deck mounts with hoists
   on side, evenly spread, all raised mounts
      16 - 2.24" / 57.0 mm guns in single mounts, 5.65lbs / 2.56kg shells, 1918 Model
   Anti-aircraft guns in deck mounts 
   on side, evenly spread, all raised mounts
 Weight of broadside 22,213 lbs / 10,076 kg
 Shells per gun, main battery: 90

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 12.0" / 305 mm 530.00 ft / 161.54 m 9.00 ft / 2.74 m
 Ends: Unarmoured
 Upper: 9.00" / 229 mm 530.00 ft / 161.54 m 8.00 ft / 2.44 m
   Main Belt covers 107 % of normal length

   - Torpedo Bulkhead:
  3.00" / 76 mm 530.00 ft / 161.54 m 30.00 ft / 9.14 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 12.0" / 305 mm 9.00" / 229 mm  12.0" / 305 mm
 2nd: 5.00" / 127 mm 5.00" / 127 mm  5.00" / 127 mm

   - Armour deck: 4.00" / 102 mm, Conning tower: 12.00" / 305 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 107,115 shp / 79,908 Kw = 27.00 kts
 Range 10,000nm at 15.00 kts
 Bunker at max displacement = 6,801 tons

Complement:
 1,521 - 1,978

Cost:
 £8.429 million / $33.714 million

Distribution of weights at normal displacement:
 Armament: 2,777 tons, 6.3 %
 Armour: 14,582 tons, 33.1 %
    - Belts: 4,065 tons, 9.2 %
    - Torpedo bulkhead: 1,765 tons, 4.0 %
    - Armament: 4,018 tons, 9.1 %
    - Armour Deck: 4,411 tons, 10.0 %
    - Conning Tower: 323 tons, 0.7 %
 Machinery: 3,864 tons, 8.8 %
 Hull, fittings & equipment: 17,089 tons, 38.8 %
 Fuel, ammunition & stores: 5,788 tons, 13.1 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   57,133 lbs / 25,915 Kg = 27.9 x 16.0 " / 406 mm shells or 8.9 torpedoes
 Stability (Unstable if below 1.00): 1.09
 Metacentric height 6.3 ft / 1.9 m
 Roll period: 17.5 seconds
 Steadiness - As gun platform (Average = 50 %): 62 %
   - Recoil effect (Restricted arc if above 1.00): 0.87
 Seaboat quality  (Average = 1.00): 1.23

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.626
 Length to Beam Ratio: 7.36 : 1
 'Natural speed' for length: 27.66 kts
 Power going to wave formation at top speed: 49 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 4.00 degrees
 Stern overhang: -2.00 ft / -0.61 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  28.00 ft / 8.53 m
    - Forecastle (20 %): 25.00 ft / 7.62 m
    - Mid (67 %):  25.00 ft / 7.62 m (17.00 ft / 5.18 m aft of break)
    - Quarterdeck (15 %): 17.00 ft / 5.18 m
    - Stern:  17.00 ft / 5.18 m
    - Average freeboard: 22.60 ft / 6.89 m
 Ship tends to be wet forward

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 93.7 %
  - Above water (accommodation/working, high = better): 170.1 %
 Waterplane Area: 59,604 Square feet or 5,537 Square metres
 Displacement factor (Displacement / loading): 99 %
 Structure weight / hull surface area: 208 lbs/sq ft or 1,014 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.98
  - Longitudinal: 1.21
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is adequate
 Room for accommodation and workspaces is excellent
 Good seaboat, rides out heavy weather easily