Commission status and information (Google Docs)
Due to the new system of adding skills, it is recommended that ALL players in the lobby have the mod. People won't crash if they don't have it, but it will quite likely render the skill ineffective.

This mod:

• Turns the Bomber Jewel 1 into the Crushing Jewel 3, which contains the brand new skill Breakthrough.
• Gives breakthrough to the following armors with the following levels:
  Diablos Vambraces S : Level 1
  Diablos Coil S : Level 1
  
• The recipe of the Crushing Jewel is as follows:
  3 Lazurite Jewels
  1 Tigrex Maw
  1 Diablos Medulla
  2 Apex Curlhorn
  (Why yes, you can always cheat by crafting them before getting the mod, but that wouldn't be fun, would it?)
  
• The recipe is unlocked upon killing Apex Diablos.
• There are 3 levels to the skill, each creating a bigger weak point.
  

Known Issues:

• Some text is missing from certain screens.
• Jewel will sometimes show its old name instead of its new name.
  

What is Breakthrough?
Taken directly from the in-game description:
Repeatedly hitting a monster part tenderizes it, negating deflects and increasing weapon effectiveness. Mind's Eye improves this effect.
Each monster part has its own buildup, which increases every time you hit it, by an amount specific to your weapon, which is improved by having any level of Mind's Eye. Once this buildup reaches the threshold, the monster part becomes weakened (signified by a change of sound on hit) for a period of time, also dependent on your weapon (30 to 60 seconds). In this weakened state, the hitzone value of that monster part increases, and if it goes above the threshold, allows triggering weakness exploit. Once the effect wears off, the part will be easier to weaken than the first time. Only one part may be weakened at a time. If enough hits are dealt to a different part during this time, the original weakened part will disappear and the newly hit part will be weakened in its stead. Buildup for all parts resets whenever one part is weakened.

What are the specific numbers?
On a per weapon basis (Duration / Required Hits):
Greatsword : 55s / 6
Longsword: 30s / 30
Sword and Shield : 30s / 20 
Dual Blades: 30s / 30
Hammer: 50s / 10
Hunting Horn: 40s / 12
Gunlance: 40s / 10
Lance: 35s / 10
Switch Axe: 40s / 15
Charge Blade: 40s / 15
Insect Glaive: 30s / 13
Light Bowgun: 30s / 20
Heavy Bowgun: 45s / 12
Bow: 35s / 17

In order to understand how the buildup works:
The threshold at all times is 100, and each hit with a weapon deals 100 / [Required Hits] buildup. With Mind's Eye, the buildup is multiplied by 1.5, and if the effect has been triggered once before, another cumulative 1.5. When the effect triggers, the hitzone is increased by the formula (100 - HZV) x [level multiplier], which for each level is 1.1, 1.15, and 1.2 respectively.

The buildup value decays by 1 per second until it reaches 0.