I updated 2 things in the original model.
1) The original model had a ring on top, to use as key-chain. But I wanted helmet only, so I removed the ring on top. Another 'ring removed' model is there but it has 'dent' on top (see image). Mine is clean ☺☺☺
2) The spikes on the helmet were just touching the helmet, which made them weaker. They came out with slight stroke. I combined them within the helmet, so now they are quite strong.
Note: You can make stand for the helmet. Download : http://www.thingiverse.com/thing:2155961