You don't need 1.26 seakeeping to get "good seaboat". 1.2 will do that just fine, and in return you'll get more cross-sectional hull strength, so you can add a bit of miscellaneous weight for anti-submarine work.
I agree that good seakeeping is important in the rough waters around southern Chile.
At the ranges destroyer combat hapens, deck hits are rare, and belt hits can't really be defended against, so deck or belt armor on a destroyer dosen't really help. Use the weight for more speed.
Capitan Herlock, Chilean/Nordmark Destroyer laid down 1914
Displacement:
1,089 t light; 1,129 t standard; 1,300 t normal; 1,431 t full load
Loading submergence 145 tons/feet
Dimensions:
315.00 ft x 28.00 ft x 11.75 ft (normal load)
96.01 m x 8.53 m x 3.58 m
Armament:
4 - 4.30" / 109 mm guns
2 - 1.46" / 37 mm guns
2 - 1.90" / 48 mm AA guns
Weight of broadside 169 lbs / 77 kg
4 - 18.0" / 457.2 mm above water torpedoes
Armour:
Conning tower 4.00" / 102 mm
Machinery:
Coal and oil fired boilers, steam turbines,
Geared drive, 2 shafts, 26,731 shp / 19,941 Kw = 31.00 kts
Range 6,700nm at 10.00 kts
Complement:
108 - 140
Cost:
£0.194 million / $0.775 million
Distribution of weights at normal displacement:
Armament: 21 tons, 1.6 %
Armour: 10 tons, 0.8 %
Belts: 0 tons, 0.0 %, Armament: 0 tons, 0.0 %, Armour Deck: 0 tons, 0.0 %
Conning Tower: 10 tons, 0.8 %, Torpedo bulkhead: 0 tons, 0.0 %
Machinery: 688 tons, 52.9 %
Hull, fittings & equipment: 320 tons, 24.6 %
Fuel, ammunition & stores: 211 tons, 16.2 %
Miscellaneous weights: 50 tons, 3.8 %
Metacentric height 1.2
Remarks:
Caution: Hull subject to strain in open-sea
Hull space for machinery, storage & compartmentation is cramped
Room for accommodation & workspaces is adequate
Ship has slow, easy roll, a good, steady gun platform
Good seaboat, rides out heavy weather easily
Estimated overall survivability and seakeeping ability:
Relative margin of stability: 1.28
Shellfire needed to sink: 292 lbs / 132 Kg = 7.3 x 4.3 " / 109 mm shells
(Approx weight of penetrating shell hits needed to sink ship excluding critical hits)
Torpedoes needed to sink: 0.2
(Approx number of typical torpedo hits needed to sink ship)
Relative steadiness as gun platform: 70 %
(Average = 50 %)
Relative rocking effect from firing to beam: 0.28
Relative quality as seaboat: 1.20
Hull form characteristics:
Block coefficient: 0.439
Sharpness coefficient: 0.30
Hull speed coefficient 'M': 8.82
'Natural speed' for length: 17.75 kts
Power going to wave formation at top speed: 66 %
Trim: 58
(Maximise stabilty/flotation = 0, Maximise steadiness/seakeeping = 100)
Estimated hull characteristics & strength:
Underwater volume absorbed by magazines and engineering spaces: 187.4 %
Relative accommodation and working space: 93.9 %
(Average = 100%)
Displacement factor: 54 %
(Displacement relative to loading factors)
Relative cross-sectional hull strength: 0.50
(Structure weight / hull surface area: 30 lbs / square foot or 147 Kg / square metre)
Relative longitudinal hull strength: 1.28
(for 13.60 ft / 4.15 m average freeboard, freeboard adjustment 3.53 ft)
Relative composite hull strength: 0.55
Good start on a difficult specification. Destroyers are a pain to simulate.