I recently played some Quake 1 addons that I had missed over the years and chose Hard mode the way I generally do. I did beat Nightmare at one point but I never really cared for the AI differences in casual play.
I did manage to get that glide after about 10 minutes of trying. I was not getting myself stuck before trying to wiggle through before. Still haven't figured out how to replicate the effect reliably but I'll keep playing with it. Thanks!