The GB/BB/1915 "BBX" design based on my August 2001 drawing

I have this drawing of the GB/BB/1915, my friend Cliff's "BBX" design, that I just ran through SpringSharp. This drawing attributes the 20in guns to the design. I used the dimensions from the drawing, estimated armor, and adjusted displacement and speed to work in SpringSharp. This is the report:

GB/BB/1915 BBX, Great Britain Battleship laid down 1915

Displacement:
 67,209 t light; 70,375 t standard; 74,300 t normal; 77,440 t full load

Dimensions: Length overall / water x beam x draught
 852.08 ft / 850.00 ft x 135.00 ft x 36.00 ft (normal load)
 259.71 m / 259.08 m x 41.15 m  x 10.97 m

Armament:
      9 - 20.00" / 508 mm guns (3x3 guns), 4,000.00lbs / 1,814.37kg shells, 1915 Model
   Breech loading guns in turrets (on barbettes)
   on centreline, evenly spread, 1 raised mount
   Aft Main mounts separated by engine room
      24 - 5.00" / 127 mm guns (12x2 guns), 62.50lbs / 28.35kg shells, 1915 Model
   Quick firing guns in turrets (on barbettes)
   on side, all forward, 4 raised mounts - superfiring
 Weight of broadside 37,500 lbs / 17,010 kg
 Shells per gun, main battery: 80

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 18.0" / 457 mm 435.00 ft / 132.59 m 17.00 ft / 5.18 m
 Ends: Unarmoured
   Main Belt covers 79 % of normal length

   - Torpedo Bulkhead:
  4.00" / 102 mm 435.00 ft / 132.59 m 35.00 ft / 10.67 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 18.0" / 457 mm 12.0" / 305 mm  18.0" / 457 mm
 2nd: 5.00" / 127 mm 5.00" / 127 mm  5.00" / 127 mm

   - Armour deck: 8.00" / 203 mm, Conning tower: 18.00" / 457 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 108,743 shp / 81,122 Kw = 25.00 kts
 Range 6,500nm at 15.00 kts
 Bunker at max displacement = 7,065 tons

Complement:
 2,249 - 2,925

Cost:
 £9.988 million / $39.950 million

Distribution of weights at normal displacement:
 Armament: 4,688 tons, 6.3 %
 Armour: 28,942 tons, 39.0 %
    - Belts: 6,201 tons, 8.3 %
    - Torpedo bulkhead: 2,253 tons, 3.0 %
    - Armament: 7,036 tons, 9.5 %
    - Armour Deck: 12,767 tons, 17.2 %
    - Conning Tower: 685 tons, 0.9 %
 Machinery: 4,119 tons, 5.5 %
 Hull, fittings & equipment: 29,460 tons, 39.6 %
 Fuel, ammunition & stores: 7,091 tons, 9.5 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   108,870 lbs / 49,383 Kg = 27.2 x 20.0 " / 508 mm shells or 20.0 torpedoes
 Stability (Unstable if below 1.00): 1.13
 Metacentric height 9.9 ft / 3.0 m
 Roll period: 18.0 seconds
 Steadiness - As gun platform (Average = 50 %): 70 %
   - Recoil effect (Restricted arc if above 1.00): 0.62
 Seaboat quality  (Average = 1.00): 1.40

Hull form characteristics:
 Hull has a flush deck
 Block coefficient: 0.630
 Length to Beam Ratio: 6.30 : 1
 'Natural speed' for length: 29.15 kts
 Power going to wave formation at top speed: 44 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 2.00 degrees
 Stern overhang: 1.00 ft / 0.30 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  31.00 ft / 9.45 m
    - Forecastle (20 %): 24.00 ft / 7.32 m
    - Mid (50 %):  24.00 ft / 7.32 m
    - Quarterdeck (15 %): 24.00 ft / 7.32 m
    - Stern:  25.00 ft / 7.62 m
    - Average freeboard: 24.64 ft / 7.51 m
 Ship tends to be wet forward

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 76.5 %
  - Above water (accommodation/working, high = better): 175.3 %
 Waterplane Area: 86,262 Square feet or 8,014 Square metres
 Displacement factor (Displacement / loading): 99 %
 Structure weight / hull surface area: 261 lbs/sq ft or 1,277 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.97
  - Longitudinal: 1.36
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is excellent
 Room for accommodation and workspaces is excellent
 Ship has slow, easy roll, a good, steady gun platform
 Good seaboat, rides out heavy weather easily