Hi Mark,
To answer your question, you can use Core4 with LSU6 , that means that you have all the choice to use any Core from 0 to 7 with any LSU from 0 to 7.
In fact, the LSU is a shared ressource that can be used with any Core, therefore even if 2 cores want to use the same LSU there is an implemented mechanism in KeyStoneI that manages this in order to have just One Core accessing to one LSU (more details in the 2.3.2.0.2 section of the SRIO UserGuide [sprugw1b]) .
Regards ,
Asma ,