Cisco WAN :: ASR1001 / Use Bandwidth Of VAI In QoS Parent Policy?

I've done a similar solution before where I put bandwidth inherit on the Dialer interface of the CPE and it inherited the ATM interface speed (the upload sync rate) and prevented the CPE from maxing out and hitting hardware queuing in the DSLAM.  I can't seem to find a way to do this downstream from our ASR1K to the customer though.
 
Platform is ASR1001 with IOS 3.7.2 or 15.2(4)S
 
Problem description:We have many xDSL users (ADSL2+ and VDSL2).  They all sync at different speeds depending on how far they are from the DSLAM.
 
Example:
 
Customer A might be connected at 40000kbps/10000kbps (VDSL2)
Customer B might be connected at 5000kbps/600kbps (ADSL)
 
When they connect and the PPPoE session comes up, the bandwidth on the Virtual Access Interface is equal to the customer's downstream sync rate, so Customer A's virtual access interface, Virtual-Access 2.13 will say 40000kbps, and Customer B's virtual access interface Virtual-Access 2.39 will say 5000kbps.Using RADIUS, we apply a sub-qos-policy-out to the PPPoE session.I want to shape the customer to 80% of their sync rate so that we do not hit interface congestion in the DSL network which makes VoIP perform poorly.I cannot use an absolute value for the shape, because the sync rate varies for each customer.The problem I have is at present the policy-map is using the interface bandwidth of Gi0/0/1 (1Gbit) instead of the bandwidth of the Virtual Access Interface.  Therefore the customer is being limited to 800Mbit which means the QoS policy will never take effect.
  
RADIUS Config Below:
 
cisco-avpair += ip:sub-qos-policy-out=QOS-POLICY-OUT-PARENT-DSL
 Class Maps
 class-map match-any QOS-CLASS-VOIP-RTP-DSL
match protocol rtp audio
match access-group name QOS-VOIP-RTP
class-map match-any QOS-CLASS-VIDEO-RTP-DSL

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