The pictures attached above are scans from Monografie Lotnicze and Polish Wings (for educational purposes only, of course).
September 39 aircraft are somewhat iconic in Poland. There was a huge flamewar in polish modelling forums , when previous IBG product- RWD-8, was released.
There was mistake in this kit- one rib in the wing was ommited. Some said it was only minor mistake, for others it was sacrilege! As a result two manufacturers released corrected wings. Similar discussion took place with Azur PZL P-11c. I'm quite convinced, that guys from IBG watched molding mastere several times to avoid such poo-poostorm.
My advice- feel free to ask in polish forums about polish aircraft.
I'm curious, if you are planning to build PZL-37 Łoś (does not matter, from IBG, or Fly). I'd like to see your stunning work.