Hej Adriano, I do some technical comparisons with the Hs 123 and other types as I agree that they are interesting. As you state; test reports and test pilot diaries are extremely rare, and that is indeed the case with Hs 123. However, I will cover the development and test history of the Hs 123 with the material that I have found. As for flight characteristics I asked several pilots who flew the Henschel, what they thought of it and got some nice answers. But that hardly qualify as the technical and fact oriented information you are looking for.
As for your question about manuals, there are a few technical Handbücher available on the Hs 123 A and B with technical drawings and specs reproduced several times in various publications. I do not see the sense in blindly reproduce that in my book. So in case you or Jukka are interested, I'd suggest you find them somewhere on the net and download them.
One place to buy them is here:
LINK
Cheers
Morten