Sunrise Seto lugguage?

Hi,
I know lugguage space is limited on many trains in Japan, some exceptions of course like Shinkansen (behind/in front of last seats in the car) and Keisei Skyliner.

What about the Sunrise Seto? Anyone know how big suitcase I can bring?

Sunrise Seto/Izumo(both are same series cars using no different) is Sleeper express(Limited Exp) train.
https://www.jr-odekake.net/train/sunriseseto_izumo/accommo.html
https://www.jr-odekake.net/train/sunriseseto_izumo/seat.html
http://www62.tok2.com/home/tsubame787/seat_285.html (open each pics)
So if booked A[A寝台] or B[B寝台] as a room are no worry
but Nobi-Nobi seat[ノビノビ座席] (flat carpet car/no bed,no door) is open keeping own spaces only
no locker and no luggage space just put ur head side.
http://blog-imgs-27-origin.fc2.com/b/o/s/boseskinhead/06112003.jpg
Nobi-Nobi is lower seat and upper seat exist if booled upper maybe hard a little.

(note)
As only using Japan Rail Pass NOT valid for B and A room car seat.
http://www.japanrailpass.net/en/about_jrp.html (read all orher notes if using)
Limited express and ordinary express :
Ordinary Car : Y
(means Nobi-Novi seat or Carpet car of Hamanasu[another Sleeper Exp])
Sleeping Car : N
(if paying possible LtdExp seat fee and sleeper fee about 8600-14000Y/oneway plus will be Y)