It recommended 5 foot deep and 36 inches wide and thats on level ground!
What would be easier and make the most sense, a 3s3p or 2s5p configuration?
That hole sounds a bit excessive to me? Is your soil type very loose sand? In my case, my soil type is fine silty loam, and the holes I drilled were 36" deep and 15" in diameter. I drilled those with a 2-man auger. My center posts are 8 foot long 3.5" schedule 40 pipe, sunk into that 36" hole with concrete. Next, the central pole of the rotating mount is a 4 foot long piece of 4.0" schedule 40 pipe, onto which the hinged frame is mounted.
I've used variations of this design for years now, and I've had zero problems. I'm on a ridgetop, and the wind storms can be scary. If you look at the Oak trees in the background, some of the storms have toppled Oaks 18" in diameter. The solar mounts sailed through all those storms for years now.
In terms of the wiring, I'd use a voltage drop calculator like this one to decide which wire to chose over what distance.
This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.
www.calculator.net
Remember that the Voc of your panels varies with the temperature, and a panel that puts out 30V in the summer might have a Voc of over 40+V in the winter. Midnight has a "string calculator" you can use to get exact values.
Go to
http://www.midnightsolar.com/, select "Products", then select "
Charge Controllers - Classics ", then select "
Classic Sizing Tool". You then input the parameters for your panels, and other data like your system voltage, and winter lows. The calculator will then spit out a number for the voltages and amperages you can expect to see. You can plug your values in to determine what will work best for you.
Here's another pic of my V1.5 arrays, that are holding three 300W panels, for 900W per array. This is my oldest rotating design, being in position now for 4 years.