4,000 tons must be a magic number

To get the benefit of destroyer-like composite strength assessment, I seemed to need to keep a scout cruiser below 4,000 tons normal displacement. I tried varying displacement and draft to see if I could squeeze out just a little more. I reduced freeboard, as I seemed to have adequate seakeeping capability. I was able to get a range of 4,200 nm and a maximum speed of 39 knots. That is with 6-5.5in, 8-57mm, 12-40mm, and 8-21in TT. It is only a marginal gain, but it still is nice. This is yet another Springsharp report:

GB/CL/1931, Great Britain Scout Cruiser laid down 1927 (Engine 1950)

Displacement:
 3,605 t light; 3,735 t standard; 3,995 t normal; 4,203 t full load

Dimensions: Length overall / water x beam x draught
 460.36 ft / 455.00 ft x 42.00 ft x 18.00 ft (normal load)
 140.32 m / 138.68 m x 12.80 m  x 5.49 m

Armament:
      6 - 5.50" / 140 mm guns (3x2 guns), 83.19lbs / 37.73kg shells, 1927 Model
   Dual purpose guns in deck mounts with hoists
   on centreline ends, majority forward, 1 raised mount - superfiring
      8 - 2.24" / 57.0 mm guns (4x2 guns), 5.65lbs / 2.56kg shells, 1927 Model
   Anti-aircraft guns in deck mounts with hoists
   on side, all amidships, all raised mounts - superfiring
      12 - 1.57" / 40.0 mm guns (6x2 guns), 1.95lbs / 0.89kg shells, 1927 Model
   Anti-aircraft guns in deck mounts 
   on side, evenly spread, 4 raised mounts
 Weight of broadside 568 lbs / 258 kg
 Shells per gun, main battery: 150
 8 - 21.0" / 533.4 mm above water torpedoes

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 4 shafts, 112,997 shp / 84,296 Kw = 38.75 kts
 Range 4,000nm at 15.00 kts
 Bunker at max displacement = 467 tons

Complement:
 250 - 326

Cost:
 £1.945 million / $7.780 million

Distribution of weights at normal displacement:
 Armament: 71 tons, 1.8 %
 Machinery: 2,493 tons, 62.4 %
 Hull, fittings & equipment: 1,041 tons, 26.1 %
 Fuel, ammunition & stores: 390 tons, 9.8 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   677 lbs / 307 Kg = 8.1 x 5.5 " / 140 mm shells or 0.3 torpedoes
 Stability (Unstable if below 1.00): 1.54
 Metacentric height 2.8 ft / 0.9 m
 Roll period: 10.5 seconds
 Steadiness - As gun platform (Average = 50 %): 52 %
   - Recoil effect (Restricted arc if above 1.00): 0.39
 Seaboat quality  (Average = 1.00): 1.04

Hull form characteristics:
 Hull has raised forecastle, rise forward of midbreak
 Block coefficient: 0.406
 Length to Beam Ratio: 10.83 : 1
 'Natural speed' for length: 21.33 kts
 Power going to wave formation at top speed: 67 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 5.00 degrees
 Stern overhang: 3.00 ft / 0.91 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  27.00 ft / 8.23 m
    - Forecastle (20 %): 23.00 ft / 7.01 m (21.00 ft / 6.40 m aft of break)
    - Mid (50 %):  19.00 ft / 5.79 m (17.00 ft / 5.18 m aft of break)
    - Quarterdeck (15 %): 15.00 ft / 4.57 m
    - Stern:  15.00 ft / 4.57 m
    - Average freeboard: 18.77 ft / 5.72 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 214.7 %
  - Above water (accommodation/working, high = better): 114.2 %
 Waterplane Area: 11,809 Square feet or 1,097 Square metres
 Displacement factor (Displacement / loading): 67 %
 Structure weight / hull surface area: 41 lbs/sq ft or 202 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.44
  - Longitudinal: 1.83
  - Overall: 0.50
 Hull space for machinery, storage, compartmentation is extremely poor
 Room for accommodation and workspaces is adequate