[galaxy-dev] setting SGE arguments in galaxy (cloudman)

I have a galaxy/cloudman cluster where I would like to pass a "-l mem_free=16G" parameter when galaxy submits the job to SGE. I've tried adding it like this: default_cluster_job_runner = drmaa://-l mem_free=16G/ (it was: default_cluster_job_runner = drmaa:/// ) but now the jobs don't even submit. Am I wiping out other important parameters? How should I do this? Thanks, Jim