fast inferencing with jena and ?

We are using jena in a semi-commercial application and have to do simple 
RDF/S inferencing on subclasses and subproperties.

We used Jena as basis for the app.

The problem with Jena is: the Model RDFS_MEM_TRANS_INF is too slow to do 
simple inference (and it was the fastest we found in jena)

It has 200ms performance of matching two small rdf instance models 
against a RDF/S ontology model (180 classes). Normal developer PC.
We did everything we could to make it faster, including prefetching all 
classes, properties, trying out different Jena inferencers, etc.

Question:
What inference engine can be plugged into Jena smoothely?

any experiences or papers about that?

any help appreciated.

cheers
Leo