Sounds OK to me.

Is it possible to keep the magic string at the same location? That way we get rid of reading the first four bytes completely. What is the argument behind reading the first four byte just to know how much to jump to?

The reason for raising this is analyze-compatibility, which I thought was the main reason for putting magic string at the end instead of the front, is completely out of the window with NifTI 2.  Furthermore, there is a need to reassign value to each byte on the header give the opportunity to rearrange the order of elements. Finally, it would be less complicated to jump a fixed number of bytes (344) to check the magic string instead of having to read the first four byte to decide what to do. Also, it is the norm to keep location of magic string fixed rather than  variable as in the proposal.

Best regards,
Cinly