it's a risk, but if you can catch any aggression or skittish behavior early on then it COULD work. then again, it only takes one bad hit to the glass to break a gar's back. personally i wouldn't do it. to be honest this sort of combo works well when the fishes start together at a smaller size and then may adjust to the others presence, in your case you are looking at two adult fishes being put together, which may likely increase the risk of problems.
hope that helps, and good luck--
--solomon
hope that helps, and good luck--
--solomon