Could be a while.

: This trick is one of the very few I think I ever discovered back playing it
: with my brother. Don't think we realized how to successfully get up into
: the top of the map, would always fall off.

Huh? Once you've managed to stay aboard, all you have to do is wait, and you reach the top. How could you "always fall off"?

: That and trying in vain to
: shoot and kill the Flood forms that spawn to freak you out at the
: beginning were favorite past times.

Testing on Easy with pistol fire, I find that those Flood can potentially be felled, but they're very resistant, and they always reanimate, after which they can't be felled again. They run off, seemingly impervious.