The prop on my hood was guillotine-prone because the plastic receiver was worn a bit. You can adjust it back and forth, so that is one option, but since this did not do the trick, I decided to take it off and install it the other way around (it's symmetrically shaped). Now the hood stays up very well.
Btw I have been advised not to simply drop the hood to close it - rather, we are supposed to lower the hood slowly by hand until it rests on the keeper, then use the heavy hand and press it closed firmly. Dropping it as a matter of practice supposedly is bad for the hood/paint? Seemed to make sense at the time, so that's how I've been doing it since.
Cees,
white 1969 280 SL