Cisco 7975 sip with multiple lines

[federico_tv]

I've copied this post here as wrong forum chosen... 

The goal is to register 7975 (sip firmware) to multiple ip pbx (not Cisco one) .

I'm able to register a single line using 

<proxy>USECALLMANAGER</proxy>

and declaring the pbx ip settings in 

<callManager>

<processNodeName>PBX_IP</processNodeName>

<etc.etc.>
</callManager>

Trying to set pbx(es) addresses into each line with

<proxy>PBX_IP</proxy>

cause each line to be stuck on "registering..."

Should I perhaps use multiple call managers istances into 

<callManagerGroup>

If yes, how to associate each line with the right call manager ?

Thank you very much.

[federico_tv]

Just realized the impossibility to use multiple "lines" config is a V.9 issue

Downgraded to V.8-5-4 I can configure all lines pointing to different accounts in different servers.

Any thought ?