Installationoptions PI 7.31 - Splitting ABAP/JAVA?

Hi Experts,

we are planning to install a PI 7.31 system

We are now running a PI 7.11 Dualstack with ABAP+JAVA.

We heard many rumors about the installation options.

In the thread below I alreay read that Dual Stack is still support with 7.31:

http://scn.sap.com/community/pi-and-soa-middleware/blog/2012/01/11/installation-options-for-process-integration-and-orchestration-use-cases

But we even heard that the ABAP and JAVA may need to be splitted - and not only on one server, but maybe even to two seperate hosts...

My question would now be:

1) Can I install a normal dual stack on one server/host doing a normal Add-In installation? This mean java is installed under /usr/sap/SID/DVEMBGS<NN>/j2ee and with one SID like PID for ABAP+JAVA or do we have to use two instance directories like DVEMBGS<NN> for ABAP and J<NN> with two different SIDs like maybe PID for ABAP and PJD for JAVA (But on one hhost)?

2) If a split is neccessary, does it allow the split on one server/host and is it only optional to install it on two host?

We are just dealing with all this split thoughts as SAP installed a SAP SEM BI 7.3 systes a half year ago and said the split of ABAP + JAVA to two different host is a must.

If you have information about this rergarding PI7.31 pls. let me also know where you found them, as I did not find anything regarding that.

Thanks.

Michael