A more capable British light cruiser is possible by 1931

By ballooning the displacement even more, a 35-knot light cruiser with 12-6in QF, 8-4in AA, 28-2pdr AA, and 16-21in TT is possible. The armour basis is still 4in and the range is now 8,200nm at 15 knots. This design, the GB/CL/1931, is roughly comparable to the Mogami class prior to being rearmed with 8in guns. This is the Springsharp report:

GB/CL/1931, Great Britain Light Cruiser laid down 1931

Displacement:
 11,644 t light; 12,052 t standard; 13,300 t normal; 14,298 t full load

Dimensions: Length overall / water x beam x draught
 626.42 ft / 625.00 ft x 61.00 ft x 24.00 ft (normal load)
 190.93 m / 190.50 m x 18.59 m  x 7.32 m

Armament:
      12 - 6.00" / 152 mm guns (4x3 guns), 108.00lbs / 48.99kg shells, 1931 Model
   Quick firing guns in turrets (on barbettes)
   on centreline ends, evenly spread, 1 raised mount - superfiring
      8 - 4.00" / 102 mm guns (4x2 guns), 32.00lbs / 14.51kg shells, 1931 Model
   Anti-aircraft guns in deck mounts with hoists
   on side, all amidships, all raised mounts - superfiring
      28 - 1.57" / 40.0 mm guns (7x4 guns), 1.95lbs / 0.89kg shells, 1931 Model
   Anti-aircraft guns in deck mounts 
   on side ends, majority aft, 3 raised mounts - superfiring
 Weight of broadside 1,607 lbs / 729 kg
 Shells per gun, main battery: 150
 16 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 4.00" / 102 mm 550.00 ft / 167.64 m 12.00 ft / 3.66 m
 Ends: Unarmoured
   Main Belt covers 135 % of normal length

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 4.00" / 102 mm 3.00" / 76 mm  4.00" / 102 mm

   - Armour deck: 2.00" / 51 mm, Conning tower: 4.00" / 102 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 141,896 shp / 105,854 Kw = 35.00 kts
 Range 8,200nm at 15.00 kts
 Bunker at max displacement = 2,246 tons

Complement:
 619 - 805

Cost:
 £5.107 million / $20.427 million

Distribution of weights at normal displacement:
 Armament: 201 tons, 1.5 %
 Armour: 2,417 tons, 18.2 %
    - Belts: 1,049 tons, 7.9 %
    - Torpedo bulkhead: 0 tons, 0.0 %
    - Armament: 372 tons, 2.8 %
    - Armour Deck: 947 tons, 7.1 %
    - Conning Tower: 48 tons, 0.4 %
 Machinery: 4,243 tons, 31.9 %
 Hull, fittings & equipment: 4,783 tons, 36.0 %
 Fuel, ammunition & stores: 1,656 tons, 12.5 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   12,129 lbs / 5,502 Kg = 112.3 x 6.0 " / 152 mm shells or 1.4 torpedoes
 Stability (Unstable if below 1.00): 1.22
 Metacentric height 3.4 ft / 1.0 m
 Roll period: 13.8 seconds
 Steadiness - As gun platform (Average = 50 %): 51 %
   - Recoil effect (Restricted arc if above 1.00): 0.37
 Seaboat quality  (Average = 1.00): 1.02

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.509
 Length to Beam Ratio: 10.25 : 1
 'Natural speed' for length: 25.00 kts
 Power going to wave formation at top speed: 60 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 3.00 degrees
 Stern overhang: -2.00 ft / -0.61 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  27.00 ft / 8.23 m
    - Forecastle (20 %): 24.00 ft / 7.32 m
    - Mid (67 %):  24.00 ft / 7.32 m (16.00 ft / 4.88 m aft of break)
    - Quarterdeck (15 %): 16.00 ft / 4.88 m
    - Stern:  16.00 ft / 4.88 m
    - Average freeboard: 21.60 ft / 6.58 m
 Ship tends to be wet forward

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 115.4 %
  - Above water (accommodation/working, high = better): 122.0 %
 Waterplane Area: 25,606 Square feet or 2,379 Square metres
 Displacement factor (Displacement / loading): 106 %
 Structure weight / hull surface area: 108 lbs/sq ft or 527 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.95
  - Longitudinal: 1.55
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent