Logicsmith Exhibition 7: Pentominous Borders

I was recently contemplating one of my logic puzzles from 2016, and this contest came about as a result.

You are to divide a 15x15 square grid into the smallest possible number of regions such that it forms a valid Pentominous Borders puzzle (that is, there is exactly one way to further divide the regions into pentominoes, regions of five cells each, so that no two congruent pentominoes, even if rotated or reflected, share an edge). Ties will be broken in favor of which puzzle has the most solutions if you disregard the rule that congruent pentominoes cannot share an edge (since such a puzzle is more likely to be interesting as a puzzle). Further ties will be broken by random.org. Consider the 5x5 examples below:
Puzzle A is outranked by puzzles B and C because it contains more regions (even though it also has more faux solutions); puzzle B is outranked by puzzle C because it has the same number of regions and fewer faux solutions (and in fact is a very boring puzzle).

Submit your puzzle to glmathgrant[at]gmail[dot]com within the next 4 weeks (before 11:59 PM Central time on February 12, 2018). You may enter multiple times; only your best valid entry will be counted. I will feature the best valid entry from every entrant on this blog, so even if you don't win, your puzzle-writing abilities will be showcased on my blog.

The winner will receive every puzzle in my Patron Puzzles for Philanthropy initiative! This means you'll get the original Patron Puzzles for Philanthropy pack (24 previously Patreon-exclusive word puzzles), the LiveJournal Logic Pack (300 logic puzzles), the Signed Magazine Four-Pack (four signed puzzle magazines), and the Section Six Six-Plus-Six Pack (12 Section Six puzzles). That's a $50.10 value! Three runners-up will receive the Patron Puzzles for Philanthropy pack, the LiveJournal Logic Pack, and the Section Six Six-Plus-Six Pack (a $20.10 value). The awarding of these prizes was made possible by a very generous donation I got last year. Of course, you can still support my chosen charities if you wish to do so, but if you can't afford such generosity, give puzzle-writing a try.

Good luck!

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