Ensuring the Bubble Door latches are in very good condition properly adjusted and engaged is important.
Some surplus UH-1's that had gone forestry logging and had large bubble windows installed on the Left side of the aircraft could prove a nuisance otherwise.
The airframes did some interesting warping and shape shifting activities and it was not unusual at all for the door to pop open if you had any significant forward speed and really liked to stay open until you slowed right down.
That amount of force that could generated by the bubble shape is pretty impressive and offers one a remedial course in aerodynamics and the way lift is generated in curved wing like surfaces.
That might be more of a concern than any sort of flutter causing wake turbulence in my way of thinking about it. The Huey door is pretty big and when it stuck out at about a 45 degree angle....and not wanting to come back in...gets your attention.