I think that the "whistling" that you heard, come from the cut edges of the upper Madstad shield. I get the same mild whistling noise... have gotten used to it through.
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Put some masking tape or electrical tape over the bottom edge of the top windshield - see if that affects the whistling.
I get a whistle between 38-45 mph.
The angle and height also affects the whistle.
I just don't drive those speeds....lol.
Cheers,
Steve
Received the replacement lower base plate from Madstadt last night. Look like what they did is just drilled larger mounting holes in the lower base plate; probably to aid in getting the bolts started while fastening it down. And will probably help in taking the "bow" out of the base plate after it has been tightened down onto the windshield mounts.