The reason the "dam piping place" recommends 4'-5' drop is they are suggesting 8" pipe and they are wanting maximum pull in a rain event without to high of velocities which for 200' of pipe 8" with a 4' drop has the velocities @ 7 FPS which doesn't sound too bad.
Also think of that siphon as a giant vacuum on the inlet side, run it wide open and fish are taking a journey, put a screen on it and fish, debris and silt are obviously getting sucked into the screen if it were a 12" pipe with a 10' drop traveling at 15feet per second. This is why I would raise the inlet to say 3'-4' off the bottom and you will still be pulling off the bottom regardless. Take a wet dry vac and a pile of shredded paper and see that the paper is gone well before the tube gets close to "bottom"
This is actually another reason I opted out of a siphoning spillway because when it's in siphon mode I didn't want all my fish plugging the screen or getting sucked to the vent screen and plugging it and walking out to an empty pond in the morning, We have rather large Bass
