This works even if you have completely cleared Neon.
Start by going up to Zeke's place. This will become your new respawn
Hop down onto the tracks just north of Zeke's building and head east
on the rails. Right up ahead is a train station. Head down to the
water just past the station. There is a broken dock in the water here
with a blast shard way out on the furthest pillar. You can grab the
shard at this point if you don't already have it.
All you need to do is to jump out onto the first pillar of the broken
dock to trigger the upcoming Reaper spawn. Just glide out to the first
pillar, then turn around and glide back onto land. You'll notice that
when you turn around to face land again, a ton of people coming
running up to meet Cole (if your Karma is Hero).
Head up the stairs to the train station up in front of you. As you run
up those stairs, five Reapers spawn on the platforms in the train
station. There will always be two on one side and three on the other,
and which side gets three is random.
Get yourself over to the side with the three Reapers and kill the two
on the other side to keep them from shooting at you. If you have the
shield, now is a good time to use it. You can somewhat position the
Reapers by moving towards or away from them. Get them into either
stairwell, as this is your key choke point to hit all three with a
It's probably easiest to head down one of the stairways towards the
street and wait near the bottom. The three Reapers will join you on
the stairs and run back and forth while shooting at you. Keep your
shield up and wait for all three to stand in the same position. Since
you can't always see all three at once, just watch for the three red
marks on your mini-map to clump up. Once that happens, immediately run
up to them and use Shockwave. If you can keep your view pointed
slighting upwards, this increases your odds.
If it went well, you will get the Have A Nice Fall stunt. If you
failed, just jump into the water and you'll immediately respawn at
Zeke's. Hop down to the tracks and head back to the train station and
I've used this and it works. There are some possible quirks. Here is a link to an archived thread discussing this method: http://www.gamefaqs.com/boards/942025-infamous/49726407
Here is an embedded video to help visualize this method: