The J/CB/1918 design has ended up being a fast battleship

The J/CB/1918 design is a fast battleship, although the armour basis is just 12in. It has the same armament as its battleship counterpart, but has a much higher speed at 32 knots. That speed was a challenge, as I struggled to reach adequate seakeeping with this design. I kept raising the freeboard and increasing the draft, almost without effect. What finally made the difference was increasing the length. By the way, for the Japanese battlecruiser series, I will be starting from the corresponding battleship and modifying the design to be a battlecruiser, rather than having a continuous series of battlecruisers. This is the Springsharp report:

J/CB/1918, Japan Battleship laid down 1918

Displacement:
 48,367 t light; 50,611 t standard; 55,800 t normal; 59,951 t full load

Dimensions: Length overall / water x beam x draught
 837.38 ft / 835.00 ft x 108.00 ft x 34.00 ft (normal load)
 255.23 m / 254.51 m x 32.92 m  x 10.36 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, 6 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 620.00 ft / 188.98 m 9.00 ft / 2.74 m
 Ends: Unarmoured
 Upper: 9.00" / 229 mm 620.00 ft / 188.98 m 8.00 ft / 2.44 m
   Main Belt covers 114 % of normal length

   - Torpedo Bulkhead:
  3.00" / 76 mm 620.00 ft / 188.98 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, 233,965 shp / 174,538 Kw = 32.00 kts
 Range 12,000nm at 15.00 kts
 Bunker at max displacement = 9,341 tons

Complement:
 1,814 - 2,359

Cost:
 £10.414 million / $41.655 million

Distribution of weights at normal displacement:
 Armament: 2,777 tons, 5.0 %
 Armour: 16,658 tons, 29.9 %
    - Belts: 4,675 tons, 8.4 %
    - Torpedo bulkhead: 2,065 tons, 3.7 %
    - Armament: 4,490 tons, 8.0 %
    - Armour Deck: 5,051 tons, 9.1 %
    - Conning Tower: 378 tons, 0.7 %
 Machinery: 8,440 tons, 15.1 %
 Hull, fittings & equipment: 20,492 tons, 36.7 %
 Fuel, ammunition & stores: 7,433 tons, 13.3 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   65,894 lbs / 29,889 Kg = 32.2 x 16.0 " / 406 mm shells or 8.8 torpedoes
 Stability (Unstable if below 1.00): 1.11
 Metacentric height 6.9 ft / 2.1 m
 Roll period: 17.3 seconds
 Steadiness - As gun platform (Average = 50 %): 52 %
   - Recoil effect (Restricted arc if above 1.00): 0.77
 Seaboat quality  (Average = 1.00): 1.04

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.637
 Length to Beam Ratio: 7.73 : 1
 'Natural speed' for length: 28.90 kts
 Power going to wave formation at top speed: 55 %
 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:  34.00 ft / 10.36 m
    - Forecastle (20 %): 29.00 ft / 8.84 m
    - Mid (67 %):  29.00 ft / 8.84 m (21.00 ft / 6.40 m aft of break)
    - Quarterdeck (15 %): 21.00 ft / 6.40 m
    - Stern:  21.00 ft / 6.40 m
    - Average freeboard: 26.76 ft / 8.16 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 106.1 %
  - Above water (accommodation/working, high = better): 192.0 %
 Waterplane Area: 68,260 Square feet or 6,342 Square metres
 Displacement factor (Displacement / loading): 100 %
 Structure weight / hull surface area: 210 lbs/sq ft or 1,025 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.98
  - Longitudinal: 1.25
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is adequate
 Room for accommodation and workspaces is excellent