An anachronistic USS Kearsarge sloop

I thought I would try my hand at an anachronistic design for the USS Kearsarge, the sloop laid down in 1861. I did some research about American guns in the Civil War time period and made some conversion decisions:

American guns

11in SB Dahlgren    7.1 tons   6in/45    7 tons
9in SB Dahlgren     4.1 tons   5in/51    4 tons
32pdr SB            2 tons     4in/50    2 tons
8in Parrott RML     7.4 tons   6in/45    7.5 tons
6.4in Parrott RML   4.4 tons   5.5in/45  4.5 tons
5.3in Parrott RML   2.4 tons   4.7in/45  2.25 tons
4.2in Parrott RML   1.56 tons  4in/40    1.5 tons

A nice feature of Springsharp 3.0, of which I just now took advantage, is that you can specify the length in calibers, as well as the bore diameter. The Kearsarge originally had 1-4.2in Parrott RML, 2-11in SB, 4-32pdr SB guns. My anachronistic design has 2-6in/45, 1-4in/40, and 4-4in/50 guns. This is the resulting Springsharp 3.0 beta design:

USS Kearsarge, anachronistic, United States Sloop laid down 1907

Displacement:
 1,245 t light; 1,309 t standard; 1,576 t normal; 1,790 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
 (216.89 ft / 214.00 ft) x 33.00 ft x (15.50 / 17.08 ft)
 (66.11 m / 65.23 m) x 10.06 m  x (4.72 / 5.21 m)

Armament:
      2 - 6.00" / 152 mm 45.0 cal guns - 108.92lbs / 49.41kg shells, 150 per gun
   Breech loading guns in deck and hoist mounts , 1907 Model
   2 x Single mounts on centreline ends, evenly spread
   Main guns limited to end-on fire
      1 - 4.00" / 102 mm 40.0 cal gun - 30.67lbs / 13.91kg shells, 150 per gun
   Breech loading gun in deck and hoist mount , 1907 Model
   1 x Single mount on centreline, aft deck aft
      4 - 4.00" / 102 mm 50.0 cal guns - 33.88lbs / 15.37kg shells, 150 per gun
   Breech loading guns in deck and hoist mounts , 1907 Model
   4 x Single mounts on sides, evenly spread
 Weight of broadside 384 lbs / 384 kg

Armour:
   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 2.00" / 51 mm       -   2.00" / 51 mm
 2nd: 2.00" / 51 mm       -   2.00" / 51 mm
 3rd: 2.00" / 51 mm       -   2.00" / 51 mm

Machinery:
 Coal fired boilers, complex reciprocating steam engines, 
 ERROR: Revise drives, 2 shafts, 5,342 ihp / 3,985 Kw = 19.00 kts
 Range 4,200nm at 12.00 kts
 Bunker at max displacement = 481 tons (100% coal)

Complement:
 124 - 162

Cost:
 £0.164 million / $0.657 million

Distribution of weights at normal displacement:
 Armament: 107 tons, 6.8 %
 Armour: 36 tons, 2.3 %
    - Belts: 0 tons, 0.0 %
    - Torpedo bulkhead: 0 tons, 0.0 %
    - Armament: 36 tons, 2.3 %
    - Armour Deck: 0 tons, 0.0 %
    - Conning Tower: 0 tons, 0.0 %
 Machinery: 592 tons, 37.5 %
 Hull, fittings & equipment: 572 tons, 36.3 %
 Fuel, ammunition & stores: 331 tons, 21.0 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   865 lbs / 393 Kg = 8.0 x 6.0 " / 152 mm shells or 0.4 torpedoes
 Stability (Unstable if below 1.00): 1.06
 Metacentric height 1.1 ft / 0.3 m
 Roll period: 13.5 seconds
 Steadiness - As gun platform (Average = 50 %): 100 %
   - Recoil effect (Restricted arc if above 1.00): 1.15
 Seaboat quality  (Average = 1.00): 1.79

Hull form characteristics:
 Hull has a flush deck,
   a normal bow and a cruiser stern
 Block coefficient (normal/deep): 0.504 / 0.519
 Length to Beam Ratio: 6.48 : 1
 'Natural speed' for length: 14.63 kts
 Power going to wave formation at top speed: 61 %
 Trim (Max stability = 0, Max steadiness = 100): 75
 Bow angle (Positive = bow angles forward): 3.00 degrees
 Stern overhang: 2.00 ft / 0.61 m
 Freeboard (% = length of deck as a percentage of waterline length):
    Fore end,  Aft end
    - Forecastle: 20.00 %,  17.00 ft / 5.18 m,  14.00 ft / 4.27 m
    - Forward deck: 30.00 %,  14.00 ft / 4.27 m,  14.00 ft / 4.27 m
    - Aft deck: 35.00 %,  14.00 ft / 4.27 m,  14.00 ft / 4.27 m
    - Quarter deck: 15.00 %,  14.00 ft / 4.27 m,  16.00 ft / 4.88 m
    - Average freeboard:  14.39 ft / 4.39 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 143.5 %
  - Above water (accommodation/working, high = better): 101.6 %
 Waterplane Area: 4,722 Square feet or 439 Square metres
 Displacement factor (Displacement / loading): 100 %
 Structure weight / hull surface area: 58 lbs/sq ft or 285 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.82
  - Longitudinal: 6.91
  - Overall: 1.01
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is adequate
 Ship has slow, easy roll, a good, steady gun platform
 Excellent seaboat, comfortable, can fire her guns in the heaviest weather