I am pretty stoked on the 2015 Zen L too... time to upgrade, as long as it fits like the 2014 zen L and NOT like the 2014 karma M. they changed the knee positioning in the Rockstar and Karma last year. I loved the shape, but my legs went numb quickly like the old EZG and 90's kayak designs we are trying to leave in the garden growing plants.......that Karma demo was very distressing to me, as otherwise JK boats have been pretty universally comfortable, and i have been able to progress, and stay all day comfortable like never before ,since 2010 and switching to JK.....This shouldn't be a problem for regular shaped i.e. petite.... people.
To decide sizes, in a nutshell i would advise you to go medium, unless you have a good reason not to. (XLarge person or big water/expedition stuff.)
I am a big boy, so Lg is definitely my choice.I also look to pack up for selfsupport as a need, and the superhero @95 gal can easily pack for a 4day trip, and still paddle like a champ...albeit a champ aircraft carrier. lol.
for reference, In my experience, (and cause they told me) JK sizes are generous, as in 2009 4fun worked for me at 230+, Karma M was brilliant except the knees.... and the 2011 superhero and 2012 superstar are my currently owned and favorite boats ever...yet.
I want 2015 L zen and 4fun if I can work it this summer. add a L rogue or XP10 and theres a quiver for you. Or me... actually
only other logical comp is a LL super squirrel, or ZET director. those are on my radar. (ZET!!!)
If you go to JK. com, email or query them on the Zen product page. - they answer size questions all year long. i bet some one asked about your size already.
I would ask Clay@jacksonkayak.com
i bet he is close to your size, and... knows some stuff.to say the least.