Thank you for your help! I have ordered the book, it looks very promising on the JADAR page! I have bought the Pegaz-bis book about the "Artyleria samobiezna w Polsich Silach Zbrojnych 1940-1945" from Jadar earlier and it has already been of much help.
Now that the new Dragon kit is arriving, I guess we will see discussions about its pros and cons here on ML. I hope that Polish modellers will contribute, you seem to have museeum examples, photos and tech manuals in Poland! And photo examples of the camoflaged ones, the camouflage pattern I find very interesting, it seems to be standardized.
Thanks again for your help,