Mash Tun question

My neighbor threw out an old 48 qt cooler that has a spigot. I snatched it up and want to make a mash tun out of it. I usually only do 5 gallon batches because thats all that my stove can support.
Should i worry about grain depth if i only use about 10lb of grain in a 48qt rectangular cooler?
I also wanted some advice regarding the manifold. I've seen copper and PVC piping and pipe braids used. What seems to be the best? Braids look like they're the easiest.
Advice is welcomed on how to build it.

That size is great and will work well. I use a stainless steel braid and have had no problems with draining. I built it just like this >> DennyBrew

Copper is fine. Don't use PVC! If you want to make a plastic manifold use CPVC.

Grain bed depth is a overblow concern.

You don't need to glue the plastic together or solder the copper. I think most people use 1/8 drill bit for the holes.

If you decide to go with mesh make sure you are getting stainless steel many places (Wal-Mart) sell plastic mesh that looks like stainless steel.