Keesje, here are some benchmark numbers for your design:
P-3C P-7A
Max Takeoff Gross Weight 139,760 lbs 171,350 lbs
Flight Design Gross Weight (3.0g) 135,000 lbs 165,000 lbs
Maneuver Weight (3.5g) --- 137,000 lbs
Design Zero Fuel Weight 77,200 lbs 105,000 lbs
Maximum Payload 22,237 lbs 38,385 lbs
Fuel Capacity 62,587 lbs 66,350 lbs
Maximum Landing Weight 114,000 lbs 144,000 lbs
Design Landing Weight 103,880 lbs 125,190 lbs
Sonobuoy Capacity 84 150-300
Wing Span 99.6 ft 106.6 ft
Wing Area 1300 sq ft 1438 sq ft
Fuselage Length* 116.8 ft 112.7 ft
Height 34.2 ft 32.9 ft
Federation of American Scientists :: P-7 Long Range Air ASW-Capable Aircraft (LRAACA)
* Hmmm, fuselage length for proposed P-7 is wrong. Wonder what else is wrong with that list?