JMZMS,

Got a couple of suggestions, sorry no answers for 1 through 4. If your going with perforated pipe there is a cloth sock that goes over the pipe to keep the dirt out. Buy 90 degree corner fittings for under your downspouts (put some crushed stone under the corner). This way you can attach a piece of the black pipe to meet the downspout. No additional wear or pressure on the corner instead of just bending the pipe and a little nicer looking job when your done.

Did a couple of drainage projects last year and rented a sod cutter to cut the path where we were going with the corrigated pipe. Rolled up the sod and put it on one side. Then rolled out lenghts of burlap on the other side of the planned path and shoveled the dirt (really clay) onto the burlap. After laying the pipe I shoveled most of the dirt back into the trench and finished up by picking up the burlap with the rest of the dirt and put it back into the trench. Very, very labor intensive job. Also used a tamper to pound the dirt down before rolling the sod back in place.

I doubt if you'll enjoy this project but I hope it all works out for you.

Regards, rredogg