The US/CL/1943 is just an incremental improvement

The main feature of the US/CL/1943 is that the armour basis is now 4.5in, instead of 4in. Otherwise, the only other changes are increased length, displacement, and freeboard. The freeboard was needed improve seakeeping without narrowing the beam further or imcreasing the draft. This is the Springsharp report:

US/CL/1943, United States Light Cruiser laid down 1943 (Engine 1950)

Displacement:
 17,647 t light; 18,267 t standard; 19,850 t normal; 21,116 t full load

Dimensions: Length overall / water x beam x draught
 698.89 ft / 694.00 ft x 65.00 ft x 26.00 ft (normal load)
 213.02 m / 211.53 m x 19.81 m  x 7.92 m

Armament:
      15 - 6.00" / 152 mm guns (5x3 guns), 108.00lbs / 48.99kg shells, 1943 Model
   Quick firing guns in turrets (on barbettes)
   on centreline ends, majority forward, 2 raised mounts - superfiring
      12 - 5.00" / 127 mm guns (6x2 guns), 62.50lbs / 28.35kg shells, 1943 Model
   Dual purpose guns in turrets (on barbettes)
   on side, all amidships
      48 - 1.57" / 40.0 mm guns (12x4 guns), 1.95lbs / 0.89kg shells, 1943 Model
   Anti-aircraft guns in deck mounts 
   on side, evenly spread, 8 raised mounts
      24 - 0.79" / 20.0 mm guns in single mounts, 0.24lbs / 0.11kg shells, 1943 Model
   Breech loading guns in deck mounts 
   on side, evenly spread, 16 raised mounts
 Weight of broadside 2,470 lbs / 1,120 kg
 Shells per gun, main battery: 150
 12 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 4.50" / 114 mm 650.00 ft / 198.12 m 16.00 ft / 4.88 m
 Ends: Unarmoured
   Main Belt covers 144 % of normal length

   - Torpedo Bulkhead:
  1.00" / 25 mm 650.00 ft / 198.12 m 25.00 ft / 7.62 m

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 4.50" / 114 mm 2.50" / 64 mm  4.50" / 114 mm
 2nd: 1.00" / 25 mm 1.00" / 25 mm  1.00" / 25 mm

   - Armour deck: 4.00" / 102 mm, Conning tower: 4.50" / 114 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 196,144 shp / 146,323 Kw = 37.00 kts
 Range 10,000nm at 15.00 kts
 Bunker at max displacement = 2,849 tons

Complement:
 836 - 1,087

Cost:
 £10.040 million / $40.160 million

Distribution of weights at normal displacement:
 Armament: 309 tons, 1.6 %
 Armour: 5,737 tons, 28.9 %
    - Belts: 1,844 tons, 9.3 %
    - Torpedo bulkhead: 601 tons, 3.0 %
    - Armament: 695 tons, 3.5 %
    - Armour Deck: 2,526 tons, 12.7 %
    - Conning Tower: 71 tons, 0.4 %
 Machinery: 4,692 tons, 23.6 %
 Hull, fittings & equipment: 6,909 tons, 34.8 %
 Fuel, ammunition & stores: 2,203 tons, 11.1 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   26,209 lbs / 11,888 Kg = 242.7 x 6.0 " / 152 mm shells or 3.1 torpedoes
 Stability (Unstable if below 1.00): 1.12
 Metacentric height 3.3 ft / 1.0 m
 Roll period: 15.1 seconds
 Steadiness - As gun platform (Average = 50 %): 52 %
   - Recoil effect (Restricted arc if above 1.00): 0.52
 Seaboat quality  (Average = 1.00): 1.05

Hull form characteristics:
 Hull has a flush deck
   and transom stern
 Block coefficient: 0.592
 Length to Beam Ratio: 10.68 : 1
 'Natural speed' for length: 29.64 kts
 Power going to wave formation at top speed: 62 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 5.00 degrees
 Stern overhang: 2.00 ft / 0.61 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  33.00 ft / 10.06 m
    - Forecastle (20 %): 25.00 ft / 7.62 m
    - Mid (67 %):  25.00 ft / 7.62 m
    - Quarterdeck (15 %): 25.00 ft / 7.62 m
    - Stern:  25.00 ft / 7.62 m
    - Average freeboard: 25.64 ft / 7.82 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 129.1 %
  - Above water (accommodation/working, high = better): 158.8 %
 Waterplane Area: 34,135 Square feet or 3,171 Square metres
 Displacement factor (Displacement / loading): 113 %
 Structure weight / hull surface area: 116 lbs/sq ft or 565 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.94
  - Longitudinal: 1.69
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent