My solution to the flutter and windshield flex issue was to fabricate a couple of aluminum tubes and a couple of aluminum brackets (see pictures). The tubes attach to the top frame at the pivot joints with simple wing nuts. The brackets attach to the header bow on either side and remain bolted in place. The tubes are removable and get installed last after the top is in place. Installation is simple, just slide them through a sleeve sewed to inside of each window opening, slide tube over nylon spacer fixed to bracket, and attach the back end of the flattened tube end with the wing nut. With this setup, I can drive at any speed with no flutter and no screen flex.... and no side curtains...
Sorry for the crappy pix, couldn't seem to eliminate the glare.