mixing MP with MPI in R?

I recently ran into a problem that was easier to solve using mutilcore
compared with Rmpi because I had a large matrix that I was performing
calculations on and it copying it for each process ate up my 12GB of memory.
I now have access to 2 Linux machine, each a core i7 with 12GB of memory,
and wonder how I might speed things up even faster by using some sort of
combination of multicore and Rmpi/snow.

I'm a novice at this, so perhaps the answer is obvious, but is it possible
to spawn to multiple machines with non-shared memory but within each machine
used shared memory? If my novice understanding is correct, the former uses
openMPI and the latter openMP.

If this is possible, a self-contained example would be appreciated, even if
the calculations are so trivial as to not make the parallelization
worthwhile in the example case