I'm about 5' 11" , even invested in a new lid, gone from an Arai astro J to a new Shoei XR1100, although the Shoei is quieter than the Arai ( not to mention the visor change mechanism that is light years ahead of the Arai ! ) the problems not actually the helmet, its the turbulent air coming off the screen.
And I don't want to start a war about which helmet is better, Arai or Shoei cos I've had 4 or 5 of each of them, I just buy what takes my fancy at the time
Sub, I actually managed to tilt the screen back a little as a test, I made a 20mm strap for the front screw fixing of the screen, took the two middle screws out altogether and let the screen tilt backwards on the two back screws.
This dropped the top edge of the screen by about 30 mm and made it a slightly shallower angle, but didn't seem to make much difference to the buffeting, I think one problem may have been that it opened up the gap slightly between the bottom of the screen and the bodywork of the bike allowing more air to "whistle" through the gap, I might try this again but with the gap sealed with foam or insulating tape to see if it quietens it down any.
I'm going to try and replicate some airflow tests by sticking on 250 mm lengths of cotton or wool or something around the leading edge of the screen at 50 mm intervals then take the bike for a ride, this should help me figure out which area or feature of the screen is causing the turbulence by seeing which ones flap the most.
I know all this sounds a bit "anal"
but if I can sort this buffeting I will be totally happy with the bike then.
Will keep you posted if I make any progress