I’m looking at some drawings for this kit that do not include cross sections. Was the hull round, making the cross sections all round circles?

http://www.geocities.com/gwmccue/index.html
See the John Holland historical website. Author Gary McCue did some fantastic work documenting what is known about John Holland, his submarines, and their contemporaries.
There are some drawings of the hull sections on the site. They appear to be all round sections.