Monk and Improved Natural Attack

[dragonmage]

What are the RAW for allowing a human monk to take the Improved Natural Attack feat (from the MM) to increase his unarmed damage. Is it allowed and if so how much does it improve his damage? Does it increase the damage per the monk chart or per the dmg chart?

 

[Dandu]

Choose one of the creature’s natural attack forms. The damage for this natural weapon increases by one step, as if the creature’s size had increased by one category: 1d2, 1d3, 1d4, 1d6, 1d8, 2d6, 3d6, 4d6, 6d6, 8d6, 12d6.
A weapon or attack that deals 1d10 points of damage increases as follows: 1d10, 2d8, 3d8, 4d8, 6d8, 8d8, 12d8.

 

[Cleon]

What are the RAW for allowing a human monk to take the Improved Natural Attack feat (from the MM) to increase his unarmed damage. Is it allowed and if so how much does it improve his damage? Does it increase the damage per the monk chart or per the dmg chart?

Firstly, it is allowed under the RAW. And I quote:

SRD Monk's unarmed strike
"A monk’s unarmed strike is treated both as a manufactured weapon and a natural weapon for the purpose of spells and effects that enhance or improve either manufactured weapons or natural weapons."

The Improved Natural Attack feat is an effect that improves a natural weapon, ergo you can get it for a monk's unarmed strike.

As for how much the damage improves, take the damage a human monk of the desired level does and increase it by one category. Since humans are Medium size, increasing one category gives it the unarmed strike damage of a Large creature. The easiest way to do this is just use the Large Monk column in the monk class description's Table: Small or Large Monk Unarmed Damage.

You could use the progression in the Improved Natural Attack feat or the table in Improving Monsters - Size Increase (they're the same progression, except the table only goes up to 2d8), but the monk class already has a damage table for Large monks, so why not use it?