JPA in Web Tier: Up from Little-G, or Down from Java EE 5 Certified?

[Doug Reeder]

I have a small web application which uses JPA from the web tier (i.e.  
I don't use any EJB).   The Java application server needs to run with  
as small a memory footprint as possible, since it will run on a VPS  
with only 96 MB of memory.

The question is: Is it easier to start with Little-G and add the  
necessary components, or start with the Java EE 5 Certified  
configuration and disable unnecessary services?

Little-G appears to come configured to support JTA transactions, but  
not JPA.  There's a plugin for "Application-Managed JPA" at www.geronimoplugins.com 
, but this only supports TopLink and RESOURCE_LOCAL transactions,  
unlike the OpenJPA and JTA support in the Java EE 5 Certified  
configuration.   Is there documentation on how OpenJPA  was integrated  
into the Java EE 5 Certified configuration?  I haven't found anything  
at openjpa.apache.org nor cwiki.apache.org.