Test Bed Ideas

[Lasivian]

Being that I recently purchased a house in AZ I have alot of empty dirt to play with. So i'm working on assembling a large test bed (at least 10x10 feet, most likely alot larger) with a overlying grid system of nylon cord, so I can record what is buried where.

So far i've thought of the following:

Clads (Dollars, Halves, Quarters, Nickels, Dimes, Pennies)
Misc Jewelry (Gold, Silver, etc. not too expensive)
A few small gold nuggets
Relics, old bullets

And misc "junk" to confuse signals, Along with covering part of the bed with iron nails (i've got a ton of space).

I've never made anything like this before, so input would be greatly appreciated. Such as the following:

How deep would you go, 8, 10, 16 inches at the deepest?
What special "situations" would you create?
What would you think of as the most difficult things to detect?
Have you seen any gold/silver objects that for some reason detected as something else that I might want to include?

thanks.

(BTW, The yard has yielded no finds worth noting however, except the air-conditioner capacitor that was tossed off the roof, heh)