Seems to be working now.

There was only a single gpugrid task to crunch. The problem was when boinc switched to the gpugrid task, it only used a single gpu while the other sat idle. I expected that other gpu to work on something else, PG for example.

Not sure what happened but now that same task (long wu) is working along side my PG task. So, both gpus are working now. Don't know what happened.

About the 'more than one wu at a time' question. How would I tell this? I just assumed 1 task/wu per line in the boinc manager.