GTM WIP Persistence iRule

We have two GTMs in a sync group that we utilize for our external DNS. We have a few WIPs on them and also use the local zonerunner for the rest of the zones. We are running version 10.2.2.

We are bringing up a new WIP that contains one Pool with two members in it. The members Juniper VPN devices, one in each Data Center. We want to load-balance between them "equally" and yet have clients persist to one side or the other. One of the issues we run into is the provider DNS load balancing. DNS requests coming from one end user can come from several different LDNS servers.

We began by utilizing static-persist load balance method at the Pool level and configuring a /24 CIDR mask for the static persist. This was giving us some desired results, however we noticed that when we manually bring a member in/out of a pool that the clients will go back to using their original member server. We do not want to have this as if they are using one VPN at that moment, we can't have them flip back over to another one until they are fully disconnected and logged out.

We then went to the level of persistence at the WIP level and setting a 10hr timer. That worked great and was almost what we wanted. The issue was we can't set a mask to use for the persistence there, it always uses a /32. That doesn't help us in the case of provider DNS load balancing.

My questions are:

1. Has the WIP level persistence changed in newer versions that we can set a CIDR mask to use?

2. Is there an iRule out there that can be used? Or do you think it's possible to write one? I looked at some of the commands, but do not see anyway to look into the persistence table to see current persistence records.

Thanks!

Jim