Eddie,
Looks like great fun man. I'm doing the same thing myself this year with my D5 on a somewhat smaller scale. With a regular drain pipe I wouldn't think you'd draw much silt, in fact, you need to raise the intake off the bottom somewhat to keep it from silting in, but with a siphon, maybe. Perf pipe might work if you did it right. I've never done this but I would think you'd need to cut the perf pipe to a particular length, then cap the open end. The total area of the holes in that length of perf pipe should add up to approx the same cross sectional area of the siphon pipe. That would give you a good velocity around the intake holes in the perf pipe. Too many holes and the velocity would go down around the holes.
I'd consider a siphon system if I were you. My pond will have a pretty good watershed feeding it and I'm going with a siphon and earth spillway for two reasons. The siphon will carry much more flow in the same size pipe than a regular thru pipe and the siphon pipe can go thru the dam near the top where there is less head pressure on the face of the dam. The siphon also functions as a regular drain pipe for steady state flows like springs, when it's not in siphon mode. I haven't installed one yet I'm just regurgitating what I've learned.
Good luck, looks great.
