As far as weight is concerned, it should be fine. Stand offs are typically good for between 25-50 lbs. Some quick math puts that that panel at around 70lbs. As long as you install properly you should be fine.
As for going to 1/4", it would be a big savings but I would recommend going to 8 total stand offs instead of 6. If you went with 3/8" material, you probably could get away with 6 stand offs and a pretty decent savings.