Air compressor lines

Just as a safety note, whatever you do, DO NOT use PVC pipe for piping up your shop.

While PVC pipe is rated to higher PSI ratings than your compressor will make, the danger is if the pipe does explode it will shatter into a million pieces and send shards of PVC flying about at high velocity. PVC is also vulnerable to getting banged by dropped tools, or you could accidently bump it with your tractor or somehting. That's just a recipe for disaster.

Copper piping would certainly work well, but it's pricey. Plain old galvanized pipe is probably what you see used most and if you setup your piping system correctly, it will last longer than you do.

There are quite a few good websites around that discuss proper piping layouts, and pay close attention to the sections about setting up the drains, angling the pipe so condensation flows to a drain, etc. This will ensure your piping will function well and last for a long time.

Also, spend the money on a good filter setup as well, especially if you intend to do any painting. Oiled compressors do let fractional amounts of oil past the rings and it gets into the air. Water will be present as well. If you don't have good filters and have a go at painting, you'll be less than pleased with the results.

Your compressor will "dance" while operating, and rubber mounts are usually suggested by most manufacturers.

I don't believe a flex line needs to be run through the wall, as rigid pipe is often installed through walls. However, as stated above, a flex line should connect the tank to the rigid lines.