Real life will never match an 2d animation model that doesn't have to conform to the needs of a real human head and doesn't ever stay consistent. Honestly I like the overall shape of your helmet better. The "rear skew" gives the helmet a nice dynamic flow to the design. It's also very subtle and minor and not worth starting over. I say just do a little bit polishing on a few of the details that bug you most and move onto the next amazing project.
Update or accessible in Windows Explorer. OmniOutliner 5 includes the best way to get your writing and outlining done: Full Screen Mode. The toolbar can disappear, too. When opening a document that has a column with both a summary and a sort order defined, the document will not become dirty on open.