Hi
Per my known, there are no some guidance about it.
And it is very not good suggestion install OCS on the SBS 2008.
I would recommend that you'd better bring up a separate physical box to install the ocs.
Some related information about it you can refer to below
http://technet.microsoft.com/en-us/sbs/cc817589.aspx
There is question about "Can I run windows small business server 2008 as a unified communications (UC) server?"
Another best suggestion, you can turn to some help from MS online service, you will get great help.
http://www.microsoft.com/online/geo/not-available.mspx
Regards!