My anachronistic Inconstant cruiser

I took the dimensions and the displacement for HMS Inconstant, laid down in 1866, and entered them into Springsharp. I gave the ship some armour, rather than leaving her unarmoured, and was able to achieve some speed and a good deal of range. Perhaps the armament is too heavy at 4-9.2in BLR, 10-6in QF, 8-4in QF, and 12-6pdr QF guns. The deck is 2in thick. I suspect that I could have had a better ship with 4-8in guns instead of the 9.2in. This is the Springsharp report:

HMS Inconstant, Great Britain 1st Class Cruiser (Unarmoured) laid down 1910

Displacement:
    4,188 t light; 4,573 t standard; 5,780 t normal; 6,745 t full load

Dimensions: Length overall / water x beam x draught
    340.59 ft / 337.33 ft x 50.25 ft x 25.50 ft (normal load)
    103.81 m / 102.82 m x 15.32 m  x 7.77 m

Armament:
      4 - 9.20" / 234 mm guns (2x2 guns), 389.34lbs / 176.60kg shells, 1910 Model
      Breech loading guns in turrets (on barbettes)
      on centreline ends, evenly spread
      Main guns limited to end-on fire
      10 - 6.00" / 152 mm guns (5x2 guns), 108.00lbs / 48.99kg shells, 1910 Model
      Quick firing guns in turrets (on barbettes)
      on side ends, majority forward, 1 raised mount - superfiring
      8 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1910 Model
      Quick firing guns in deck mounts with hoists
      on side, evenly spread, all raised mounts
      12 - 2.24" / 57.0 mm guns in single mounts, 6.00lbs / 2.72kg shells, 1910 Model
      Breech loading guns in deck mounts
      on side, evenly spread, all raised mounts
    Weight of broadside 2,965 lbs / 1,345 kg
    Shells per gun, main battery: 150

Armour:
   - Belts:        Width (max)    Length (avg)        Height (avg)
    Ends:    Unarmoured

   - Torpedo Bulkhead:
        1.00" / 25 mm    260.00 ft / 79.25 m    24.00 ft / 7.32 m

   - Gun armour:    Face (max)    Other gunhouse (avg)    Barbette/hoist (max)
    Main:    4.00" / 102 mm    3.00" / 76 mm        4.00" / 102 mm
    2nd:    3.00" / 76 mm    2.00" / 51 mm        3.00" / 76 mm
    3rd:    2.00" / 51 mm          -            2.00" / 51 mm
    4th:    1.00" / 25 mm          -                  -

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

Machinery:
    Oil fired boilers, steam turbines,
    Direct drive, 2 shafts, 14,500 shp / 10,817 Kw = 21.00 kts
    Range 7,700nm at 15.00 kts
    Bunker at max displacement = 2,172 tons

Complement:
    330 - 430

Cost:
    £0.541 million / $2.165 million

Distribution of weights at normal displacement:
    Armament: 370 tons, 6.4 %
    Armour: 1,096 tons, 19.0 %
       - Belts: 0 tons, 0.0 %
       - Torpedo bulkhead: 231 tons, 4.0 %
       - Armament: 431 tons, 7.5 %
       - Armour Deck: 406 tons, 7.0 %
       - Conning Tower: 28 tons, 0.5 %
    Machinery: 599 tons, 10.4 %
    Hull, fittings & equipment: 2,122 tons, 36.7 %
    Fuel, ammunition & stores: 1,592 tons, 27.6 %
    Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
    Survivability (Non-critical penetrating hits needed to sink ship):
      5,717 lbs / 2,593 Kg = 14.7 x 9.2 " / 234 mm shells or 1.5 torpedoes
    Stability (Unstable if below 1.00): 1.01
    Metacentric height 1.8 ft / 0.6 m
    Roll period: 15.7 seconds
    Steadiness    - As gun platform (Average = 50 %): 51 %
            - Recoil effect (Restricted arc if above 1.00): 1.02
    Seaboat quality  (Average = 1.00): 1.02

Hull form characteristics:
    Hull has a flush deck
    Block coefficient: 0.468
    Length to Beam Ratio: 6.71 : 1
    'Natural speed' for length: 18.37 kts
    Power going to wave formation at top speed: 53 %
    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:        18.00 ft / 5.49 m
       - Forecastle (20 %):    12.00 ft / 3.66 m
       - Mid (50 %):        12.00 ft / 3.66 m
       - Quarterdeck (15 %):    12.00 ft / 3.66 m
       - Stern:        12.00 ft / 3.66 m
       - Average freeboard:    12.48 ft / 3.80 m
    Ship tends to be wet forward

Ship space, strength and comments:
    Space    - Hull below water (magazines/engines, low = better): 139.2 %
        - Above water (accommodation/working, high = better): 76.0 %
    Waterplane Area: 10,977 Square feet or 1,020 Square metres
    Displacement factor (Displacement / loading): 110 %
    Structure weight / hull surface area: 113 lbs/sq ft or 553 Kg/sq metre
    Hull strength (Relative):
        - Cross-sectional: 0.89
        - Longitudinal: 2.79
        - Overall: 1.00
    Hull space for machinery, storage, compartmentation is cramped
    Room for accommodation and workspaces is cramped

I did some experimentation, and the result is that we might have achieved 22 knots, if we accepted 8in guns.