If I may comment, the helmet seems a bit too big.
Remember that the back part should be removable, so it gives bigger access for the head.
However if you decided to keep this, add inner crown to lift the helmet higher.
Burn those rough edges (but be careful with open fire). Either you have dull knife (replace or sharpen it JFcustom style), or keep cutting you several times in the same line.
See my tips for those things I mentioned.
Clean seam, nice!!!