I've added/removed foam from the same gap between shield/dash,,, No difference in sound.
Depending on your 'squeak', you may tighten the 'bracket to bracket' bolts and reduce/eliminate that particular noise.
I get a 'high speed wind over a screen' type of whistle at speed with the shield standing up at 60 degrees. Tilt it back and/or /tilt it back pick it up gets rid of the 'screen whistle' for me. Doesn't happen unless its upright and 'down-ish'