Surfing Waves

I'm trying to install the Block Surf single soft racks and even with the "twist hack", the buzzing sound appears whenever I drive faster than 30mph.

Did you execute the twist incorrectly? Please point out if this is the case.

Other potential issues I can think of:
(1) Racks+board on one the driver side of the roof, not centered (and this is due to the antenna thing)
(2) The two racks are too far/narrow apart?

Pictures attached.

The "secret" soft rack trick of getting rid of the "buzzing sound" is by putting a Twist in the straps. It does not mean to put a knot ( or knots ), which it looks like you've done. All you do is give the strap a simple twist / spin a half turn.