Now, a small trial with STUNTS. I´ve got different results. I think Timo was correct.
BUFFERS=99,8 51 seconds
BUFFERS=40,8 50 seconds
BUFFERS=32,8 50 seconds
BUFFERS=30,8 76 seconds
BUFFERS=20,8 118 seconds
BUFFERS=10,8 135 seconds
The golden number was 32, this time, maybe because...