While summoning or summoned armor stands tags do not effect

I tried to summon an armor stand with hands /summon ArmorStand ~ ~ ~ {showArms:1} but when I summoned it didn't have hands shown. Then I tried the same thing but withnoGravity:1 but when i punched blocks beneath it it fell down. then i tried /entitydata but the same problem.. I think this problem might me only with some tags because i have seen others summoning armor stands with tags like invisible:1 or equipment etc.