Possible to Re-Rig a HeadHacked model with Working Flex?

Title says it all, I’m trying to rig a model to the ValveBiped rig. But its just so terrible, I hate doing it. And I’m wondering if I could re-rig the head with something Maxs Biped with Working Face Flex/Eye posing?
For now I’ll have to deal with the Valve rig.

as long as you don’t move the head it should be fine

Alright so after rigging and all I get this

https://puu.sh/rYN4g/22a7aebf31.jpg

I suspect I messed up the head. But all I did was just re-rig it. I didn’t move anything but other mesh to match the head position
So I import the .VTA and the flex is completelly fucked.

is the head a separate smd

Yeah, I just re-rigged the head itself and exported it to test it

idk then, shouldnt be giving that error
maybe it’s your compiler

I tried Crowbar and Notepad++ When I import the .VTA into Max, (idk if this is an issue with Wallworm) but the Flex is completelly destroyed.
If this is unavoidable, is there any easy way to rig a model with the Valve bones without ruining the Player/NPC animations (gmod)?

Looks like you need to reduce the amount of polygons you have on the head model.