First of all: thanks for all the replies!
I find it incredibly interesting to ponder about these subjects, so more info is
better :-)
I also like the Ls-6 story!

My tendency with the B4 is to approach with too much velocity, often 100 km/h.
This gives me the feeling I have proper aileron control, so it's intentional.
When I approach the deck and slowly start to bring the nose up, I encounter the
ground effect that the B4 has. I either float for a long time before touching down
with a two-point landing, or I make a touchdown on the main wheel only (sometimes
with a slight jump after that).
What happened yesterday, was that I was so busy compensating for crosswind (I
don't want to have a traversed landing), that started floating again and gained
some altitude (1 meter roughly).
Knowing that the fault is probably in the velocity, I approached the instructor to
learn from his B4 experience.
I agree that the B4 is very friendly and benign. I will put effort in bringing my
approach speed down to 90 in the upcoming flights.