Having Problems Finding the Middle of a Monogatari story placement...

(according to the writer's intentions)

Every watch order list I've ever seen (or can currently google up) has put Hana after the second season. Likewise, it's hard to say what the author's intentions actually are- the original works never really followed a cohesive order (and certainly didn't follow the internal chronology), while the anime (barring some of the release delays mentioned in the link above) is generally considered to polish up the content order for a much more solid presentation. [This isn't actually unusual- often anime are a way for an author to create a 'definitive' version of their work.]
Keep in mind also that the anime modifies the presentation to match the release order, so going out of release order may actually weaken the narrative for you, rather than positively affect it. Though, as I (vaguely) recall, Hana is more of a side-story, anyway, so there may not be much cause to stress over its placement, either way.

Monogatari Series Second Season.

Starting August 20th, The chronology for these is as follows:
Kabukimonogatari; 8th novel. Occurs August 20th - 21st
Onimonogatari; 11th novel. August 21st to August 23rd,
Nekomonogatari: 7th novel. August 21st - 24th.
Otorimonogatari; 10th novel. October 31st - November 2nd.
Koimonogatari; 12th novel. January 1st - February 1st
Tsukimonogatari; 13th novel. Occurs February 13th - 14th.
Hanamonogatari; 9th novel. Occurs April 10th - 21st. This is part of Second Season, but is the final event chronologically.
[Version of list including content spoilers: >>]