Ah yay! I had to open all week at the store, so I had no time to work on this. Until today, when I had a revelation! And got the particles to behave in like 5 minutes! So, here's a small, yet substantial update that I hope everyone will enjoy.
Of course, after recording and compressing the movie, I realized that I didn't demo the gravlift actually working... but the down one isn't tweaked perfectly yet, so I can hold off until that bit is sorted out.
HL2: PNC Plaza 1 Gravlift Demo