7941/7961 register with two different servers on separate line keys

So I have just acquired a few 7961 phones and have them fully working with my freepbx install royal pain but got the configs all set up. So I have two Freepbx servers at two locations that are connected together with site to site vpn tunnel. We have many 7960 phones and the way they are set up is half the lines are registered to one server and the other half are registered to the other server so you can see where the calls are coming from regardless of which phone you are at or location your in. So what I cannot figure out how to do is make the 7961 do this. I am using the most up to date firmware which is 9.4(2)SR1 the newer firmwares under the line configs require you to put USECALLMANAGER and then it defaults to using the server address

So how do you get say line 2 to register to a different server that is not defined in the process node name tag is there another tag that can be added for this in the line config settings or will I have to go back to a version 8 firmware that does not require the phone to have the USECALLMANAGER setting in the proxy tag under the line options. However I think the phone would then be using UDP vs the TCP as it does in the newer options. Any help on this would be greatly appreciated thank you again.