Java EE (Java Enterprise Edition) General Discussion

Am planning to use JMS/MDB as a mechanism for legal multithreading within EE 5 container. Some of the objects carry a huge dataload however, and marshal/unmarshal may become an issue. The question is: Do appservers have the smarts NOT to serialize/deserialize objects, simply pass by reference, IF there are enough mdb's in the pool available? (Only serialize if jobs get "backed up".)
Is there a better way of doing multithreading using the EE 5 spec? (I understand that ejb automatically multithreads requests, but I have requests that do a lot of statistical work, and that one request benefits tremendoulsy by using multiple threads.)
Thanks;
nat