I took the plastic piece out that the bar sits in, rotated it 180 degrees and re-installed it. You can also ream it out just a bit to make it more 'pronounced'. Finally, you can position it in slightly different spots. In all, I managed to configure it so that the hood stays up securely. It did take some fiddling, so try these things and see if that does the trick.
Cees Klumper in Amsterdam
'69 white 280 SL automatic