A small British armoured cruiser: GB/CA/1902

I have this sketch of a small British armoured cruiser that I drew in early 1999:

My original specification now seems flawed:

Displacement: 13,600 tons
Length:          425ft
Beam:             70ft
Draft:            20ft
Cp:                0.57
Cm:                0.92

One problem is that with the specified prismatic coefficient and midships coefficient, the displacement is much too low. I immediately had to increase the draft to 23ft. That would only enable me to obtain a speed of 21 knots, using coal-fired boilers and complex reciprocating machinery. The main issue is the short length makes a higher speed difficult, given the armament and armour. This is the Springsharp report (sadly, Springsharp reports do not work well with this blog template):

GB/CA/1902, Great Britain Armoured Cruiser laid down 1902

Displacement:
 10,228 t light; 10,682 t standard; 12,551 t normal; 14,047 t full load

Dimensions: Length (overall / waterline) x beam x draught (normal/deep)
 (432.00 ft / 425.00 ft) x 70.00 ft x (23.00 / 25.31 ft)
 (131.67 m / 129.54 m) x 21.34 m  x (7.01 / 7.72 m)

Armament:
      4 - 9.20" / 234 mm 45.0 cal guns - 380.00lbs / 172.37kg shells, 90 per gun
   Breech loading guns in turret on barbette mounts, 1902 Model
   4 x Twin mounts on centreline ends, evenly spread
      14 - 6.00" / 152 mm 45.0 cal guns - 108.92lbs / 49.41kg shells, 150 per gun
   Quick firing guns in casemate mounts, 1902 Model
   14 x Single mounts on sides amidships
  8 hull mounts in casemates- Limited use in heavy seas
      Weight of broadside 3,045 lbs / 1,381 kg