Can I influence the bone envelopes? I was hoping I could get some help here.
Is there any way to influence the bone envelopes?

My Problem:
I have an Armature and the Armature is set in stone and can't be changed.
I have also an Avatar that is rigged to this Armature.

Now, I want to make a cloth item for said avatar. The problem is, automatic weights are too inaccurate for the given armature. And the bone envelopes are too big to help here. I found the settings for the envelopes but it seems they only influence them as a whole.
E.G. if I shrink the "distance" it shrinks the influence as a whole.

Maybe someone has an idea how to influence the distance in an x or y axis only ?
Pointers would be greatly appreciated!
You can't modify the bone envelope's scale at individual axis, separately. 

A bone's envelope distance is stored as a single attribute envelope_distance, without any way to modify it for a single axis. This is unlike b-bone scale which is stored separately in bbone_x and bbone_z, thus can be scaled separately. 

Your only choice here is through weight painting, already elaborated in the other answers posted before mine.