Using iRule for Carp profile persistent while using an iRule for virtual server assignation : Possible ?

Hello,

We have the following setup:

A/B VIP with a persistent profile (Carp iRule) which as a pool assigned. This vip is part of the Common Partition.

The pool as two members

1. A VIP1 defined on the same F5 instance in partition "part1"
2. B VIP2 defined on the same F5 instance in partition "part2"

we want to change the ratio of the members to decide the % of the traffic we have between A and B environment.

the following Carp iRule is used to make sure that once a user start using the new environment (A taking 100% traffic, all user are hitting A. % is increased to 20% B and 80% A. All user now hitting the B environment should stick to the B environment.

Carp Irule is defined as follow.

when CLIENT_ACCEPTED {
     TCP::collect
}

when CLIENT_DATA {
   set sid [findstr [TCP::payload] "" 5 ""]
   log local0. "UNIQUE USER ID: | $sid"

   persist hash $sid 
   TCP::release

}

My first attempt at the virtual server iRule was this, which doesn't work since I'm basically creating a round robin between the two VIPs instead of using the pool ratio mode.

when RULE_INIT {
  set ::NEXT_POOL 0  
}

when CLIENT_ACCEPTED {
  if { $::NEXT_POOL == 0 } {
    virtual a_vs
    set ::NEXT_POOL 1
  } else {
    virtual b_vs
    set ::NEXT_POOL 0
  }
}