I've updated to FW 2.0 and it worked pretty well. Peak Delta angle in Roll axis was around 1.4 degrees. Then I connected BGC Board with MK FC (Version 2.2, FW 0.9h) to get better results. . I defined roll and pitch in FC with the same parameters. No filtering, low gain and checked with a standard servo, that max movement was around 30 degrees.
After performing AUTO function for External FC gain in both axis I got every time a value of around 20 for Roll and 0 for Pitch axis !? The peak delta for roll axis decreased to 0.6 degrees. Great! But Pitch axis was bad. Peak delta around 20 degrees! Even when I tried to set External FC Gain for Pitch manually to values from -20 to 20, almost no changes. After setting gain in FC to 0, pitch axis had the same peak delta of around 1.8 degrees than before connecting GBC board to FC.