A way for Junk weight to be reduced by Pack Rat

[teppuM]

"Junk items you carry count as half of their listed weight." The built-in junk carrying is extremely cool and I love it, but this perk means that it can potentially weigh half as much. A way to modify the weight of junk carried would be wonderful for making this perk automatically take effect.
I don't know how it works internally, but it seems to be X*2=junk weight automatically? If there were a way to change the value of 2, whether by modifier or something else for a character, that would be a cool way to work it.