Assuming each Streak LRM tube is 400kg rather than 200 (following the doubled weight that the Streak SRMs have) and the same missile mass, the Kitsune could have a Streak LRM-6 with 16 rounds. More than enough, I think, for a streak system.
Playing with this, I'm somewhat undecided if the ERML should be put into a main gun or if the armor from that should just be placed into the torso and legs, with everything torso mounted.
I've tried putting them into actual stat blocks. How does this look?
ProtoMech Technical Readout
Type/Model: Kitsune (Standard)
Tech: Clan / 3090
Config: ProtoMech
Rules: Level 4, Experimental design
Mass: 14 tons (14,000 kg)
Chassis: Advanced Composite
Power Plant: 85 Size Fusion
Walking Speed: 54.0 km/h
Maximum Speed: 86.4 km/h (107 km/h)
Armor Type: Integral Advanced Alloy
Armament:
1 ER Medium Laser
1 Streak LRM-6
Manufacturer: Unknown
Location: Unknown
Communications System: Unknown
Targeting & Tracking System: Unknown
------------------------------------------------------
Type/Model: Kitsune
Mass: 14 tons (14,000 kg)
Equipment: Mass, kg
Int. Struct.: 36 pts Advanced Composite 1,400
Engine: 85 Size Fusion 2,500
Walking MP: 5
Running MP: 8 (10)
Jumping MP: 0
Heat Sinks: 5 Compact ProtoMech 1,250
Cockpit, Life Support, Sensors & Pilot: 750
Armor Factor: 71 pts Integral Advanced Alloy 3,550
Internal Armor
Structure Value
Head: 4 9
Torso: 14 28
Legs: 16 28
Main Gun: 2 6
Weapons and Equipment Location Heat Ammo Mass, kg
----------------------------------------------------------
1 ER Medium Laser Main Gun 5 0 2,250
1 Streak LRM-6 Torso 0 16 3,200
1 Protomech Myomer Booster Torso - - 350
----------------------------------------------------------
TOTALS: 0 14,000
Mass remaining, kg: 0 left
Also, since I don't think 24 rounds is really needed for a streak LRM, I figured the Harbinger setup could be done with the base Kitsune 14 ton model.
ProtoMech Technical Readout
Type/Model: Kitsune 2
Tech: Clan / 3090
Config: ProtoMech
Rules: Level 4, Experimental design
Mass: 14 tons (14,000 kg)
Chassis: Advanced Composite
Power Plant: 60 Size Fusion
Walking Speed: 42.8 km/h
Maximum Speed: 64.2 km/h
Jump Jets: 6 Improved ProtoMech Jump Jets
Jump Capacity: 180 meters
Armor Type: Integral Advanced Alloy
Armament:
1 ER Medium Laser
1 Streak LRM-5
Manufacturer: Unknown
Location: Unknown
Communications System: Unknown
Targeting & Tracking System: Unknown
------------------------------------------------------
Type/Model: Kitsune
Mass: 14 tons (14,000 kg)
Equipment: Mass, kg
Int. Struct.: 36 pts Advanced Composite 1,400
Engine: 85 Size Fusion 1,000
Walking MP: 4
Running MP: 6
Jumping MP: 6
Heat Sinks: 5 Compact ProtoMech 1,250
Cockpit, Life Support, Sensors & Pilot: 750
Armor Factor: 71 pts Integral Advanced Alloy 3,550
Internal Armor
Structure Value
Head: 4 9
Torso: 14 28
Legs: 16 28
Main Gun: 2 6
Weapons and Equipment Location Heat Ammo Mass, kg
----------------------------------------------------------
1 ER Medium Laser Main Gun 5 0 2,250
1 Streak LRM-6 Torso 0 16 2,714
JumpJets: 6 - 200 kg 1,800
----------------------------------------------------------
TOTALS: 0 14,000
Mass remaining, kg: 36 left
I think you made a mistake with your Harbinger calculations. A 4 walking MP should give you 6 running MP, so the engine rating should be 60.