A couple thoughts since there are already so many good suggestions from many others.

If you get hand cramps after 1/2 hour, it's the way you grasp the pen and not the pen itself. I usually write all weekend and never get any cramps after I changed my grip. Before I changed my grip I could hardly write a page before I would get cramps. While I know your question is about writing during your exams, you're unlikely to want to do something like changing your grip. Consider it after the examines.

The Sailor KOP nib and section is huge. Be careful because it might not fit in the Pineider ink filler.