An anachronistic torpedo-ram Polyphemus

I tried to design an anachronistic version of the torpedo-ram Polyphemus. Mine, given the later building date can make a maximum speed of 21 knots. The range is 3,200nm at 14 knots. My ship still has coal-fired boilers and reciprocating engines. The protection is a 3in deck. The ship might well have benefitted from torpedo bulkheads, but this version lacks them. This is the Springsharp report:

Polyphemus, Great Britain Torpedo-Ram laid down 1907

Displacement:
 2,090 t light; 2,141 t standard; 2,535 t normal; 2,850 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
 (264.00 ft / 254.00 ft) x 40.00 ft x (20.50 / 22.24 ft)
 (80.47 m / 77.42 m) x 12.19 m  x (6.25 / 6.78 m)

Armament:
      6 - 1.00" / 25.4 mm 45.0 cal guns - 0.50lbs / 0.23kg shells, 350 per gun
   Quick firing guns in deck and hoist mounts , 1907 Model
   2 x Single mounts on centreline ends, evenly spread
   4 x Single mounts on sides, evenly spread
 Weight of broadside 3 lbs / 3 kg
 5 - 14.0" / 356 mm above water torpedoes

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

   - Armour deck: 3.00" / 76 mm, Conning tower: 6.00" / 152 mm

Machinery:
 Coal fired boilers, complex reciprocating steam engines, 
 ERROR: Revise drives, 2 shafts, 9,717 ihp / 7,249 Kw = 21.00 kts
 Range 3,200nm at 14.00 kts
 Bunker at max displacement = 710 tons (100% coal)

Complement:
 178 - 232

Cost:
 £0.224 million / $0.894 million

Distribution of weights at normal displacement:
 Armament: 1 tons, 0.0 %
 Armour: 414 tons, 16.3 %
    - Belts: 0 tons, 0.0 %
    - Torpedo bulkhead: 0 tons, 0.0 %
    - Armament: 37 tons, 1.5 %
    - Armour Deck: 353 tons, 13.9 %
    - Conning Tower: 24 tons, 0.9 %
 Machinery: 1,071 tons, 42.2 %
 Hull, fittings & equipment: 604 tons, 23.8 %
 Fuel, ammunition & stores: 446 tons, 17.6 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   1,313 lbs / 595 Kg = 12.2 x 6 " / 152 mm shells or 0.5 torpedoes
 Stability (Unstable if below 1.00): 1.40
 Metacentric height 2.3 ft / 0.7 m
 Roll period: 11.1 seconds
 Steadiness - As gun platform (Average = 50 %): 64 %
   - Recoil effect (Restricted arc if above 1.00): 0.00
 Seaboat quality  (Average = 1.00): 1.13

Hull form characteristics:
 Hull has raised forecastle,
   a ram bow and a round stern
 Block coefficient (normal/deep): 0.426 / 0.442
 Length to Beam Ratio: 6.35 : 1
 'Natural speed' for length: 15.94 kts
 Power going to wave formation at top speed: 59 %
 Trim (Max stability = 0, Max steadiness = 100): 56
 Bow angle (Positive = bow angles forward): 0.00 degrees
 Stern overhang: 0.00 ft / 0.00 m
 Freeboard (% = length of deck as a percentage of waterline length):
    Fore end,  Aft end
    - Forecastle: 25.00 %,  18.00 ft / 5.49 m,  17.00 ft / 5.18 m
    - Forward deck: 30.00 %,  9.00 ft / 2.74 m,  9.00 ft / 2.74 m
    - Aft deck: 30.00 %,  9.00 ft / 2.74 m,  9.00 ft / 2.74 m
    - Quarter deck: 15.00 %,  9.00 ft / 2.74 m,  9.00 ft / 2.74 m
    - Average freeboard:  11.10 ft / 3.38 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 137.1 %
  - Above water (accommodation/working, high = better): 52.0 %
 Waterplane Area: 6,361 Square feet or 591 Square metres
 Displacement factor (Displacement / loading): 98 %
 Structure weight / hull surface area: 54 lbs/sq ft or 262 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.88
  - Longitudinal: 3.01
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is cramped