An Italian light cruiser

I am running into the usual problem: the Springsharp empirical formula requires too much power to reach a speed, in this case 35 knots. I have my 1928 Italian light cruiser design, and it can only reach 35 knots, when I would expect a higher speed than that. The ship has 8-6in QF guns, 4-4in AA guns,and 4-21in TT. The armour basis is 2in with a 1in deck. This is the Springsharp report:

It/CL/1928, Italy Light Cruiser laid down 1928 (Engine 1945)

Displacement:
 6,932 t light; 7,152 t standard; 7,600 t normal; 7,958 t full load

Dimensions: Length overall / water x beam x draught
 558.98 ft / 555.00 ft x 50.00 ft x 18.00 ft (normal load)
 170.38 m / 169.16 m x 15.24 m  x 5.49 m

Armament:
      8 - 6.00" / 152 mm guns (4x2 guns), 108.00lbs / 48.99kg shells, 1928 Model
   Quick firing guns in turrets (on barbettes)
   on centreline, all forward, 2 raised mounts - superfiring
      4 - 4.00" / 102 mm guns in single mounts, 32.00lbs / 14.51kg shells, 1928 Model
   Anti-aircraft guns in deck mounts with hoists
   on side, all aft
 Weight of broadside 992 lbs / 450 kg
 Shells per gun, main battery: 120
 4 - 21.0" / 533.4 mm above water torpedoes

Armour:
   - Belts:  Width (max) Length (avg)  Height (avg)
 Main: 2.00" / 51 mm 410.00 ft / 124.97 m 12.00 ft / 3.66 m
 Ends: Unarmoured
   Main Belt covers 114 % of normal length
   Main belt does not fully cover magazines and engineering spaces

   - Gun armour: Face (max) Other gunhouse (avg) Barbette/hoist (max)
 Main: 2.00" / 51 mm 1.00" / 25 mm  2.00" / 51 mm

   - Armour deck: 1.00" / 25 mm, Conning tower: 3.00" / 76 mm

Machinery:
 Oil fired boilers, steam turbines, 
 Geared drive, 2 shafts, 105,898 shp / 79,000 Kw = 35.00 kts
 Range 4,500nm at 15.00 kts
 Bunker at max displacement = 806 tons

Complement:
 406 - 529

Cost:
 £2.754 million / $11.014 million

Distribution of weights at normal displacement:
 Armament: 124 tons, 1.6 %
 Armour: 950 tons, 12.5 %
    - Belts: 399 tons, 5.3 %
    - Torpedo bulkhead: 0 tons, 0.0 %
    - Armament: 173 tons, 2.3 %
    - Armour Deck: 352 tons, 4.6 %
    - Conning Tower: 25 tons, 0.3 %
 Machinery: 2,674 tons, 35.2 %
 Hull, fittings & equipment: 3,184 tons, 41.9 %
 Fuel, ammunition & stores: 668 tons, 8.8 %
 Miscellaneous weights: 0 tons, 0.0 %

Overall survivability and seakeeping ability:
 Survivability (Non-critical penetrating hits needed to sink ship):
   6,134 lbs / 2,782 Kg = 56.8 x 6.0 " / 152 mm shells or 0.9 torpedoes
 Stability (Unstable if below 1.00): 1.15
 Metacentric height 2.3 ft / 0.7 m
 Roll period: 13.8 seconds
 Steadiness - As gun platform (Average = 50 %): 56 %
   - Recoil effect (Restricted arc if above 1.00): 0.51
 Seaboat quality  (Average = 1.00): 1.12

Hull form characteristics:
 Hull has rise forward of midbreak
 Block coefficient: 0.533
 Length to Beam Ratio: 11.10 : 1
 'Natural speed' for length: 23.56 kts
 Power going to wave formation at top speed: 62 %
 Trim (Max stability = 0, Max steadiness = 100): 50
 Bow angle (Positive = bow angles forward): 2.00 degrees
 Stern overhang: 3.00 ft / 0.91 m
 Freeboard (% = measuring location as a percentage of overall length):
    - Stem:  28.00 ft / 8.53 m
    - Forecastle (20 %): 26.00 ft / 7.92 m
    - Mid (33 %):  26.00 ft / 7.92 m (18.00 ft / 5.49 m aft of break)
    - Quarterdeck (15 %): 18.00 ft / 5.49 m
    - Stern:  18.00 ft / 5.49 m
    - Average freeboard: 20.80 ft / 6.34 m

Ship space, strength and comments:
 Space - Hull below water (magazines/engines, low = better): 126.5 %
  - Above water (accommodation/working, high = better): 157.8 %
 Waterplane Area: 19,053 Square feet or 1,770 Square metres
 Displacement factor (Displacement / loading): 104 %
 Structure weight / hull surface area: 90 lbs/sq ft or 437 Kg/sq metre
 Hull strength (Relative):
  - Cross-sectional: 0.93
  - Longitudinal: 2.05
  - Overall: 1.00
 Hull space for machinery, storage, compartmentation is cramped
 Room for accommodation and workspaces is excellent