When putting up our last grain bin I plumbed pex from our shop to the bin site. Just let it lay on ground. Rolled it back up when done. We used enough air that I had piggy-backed our 5.5 hp gasoline portable compressor into the system w/our 5 hp elec shop compressor, which is 100' away in another building anyway. Both compressors ran hard & often keeping up w/multitude of air-impacts. I'd assume one could piggy back compressors 'til you run out of room. No problems w/anything.

I agree also about needing some type of metal coupling from compressor to tank. Never seen pex or plastic used there. I've used flex stainless steel in the past....or alum tubing. Copper works also. Then I use 1.25" NH3 hose to hook compressor tank (60 gal) to system. I also have a 500 gallon air supply tank in the system. It's a former LP tank that I plumbed for air...has water drain in bottom etc.

I'd probably not use pex if lines are getting hot. Our lines don't get hot....compressor heads & manifolds do, but not our air lines. Actually, ours get cold in the winter time w/compressor running. But-that's due to compressor being located in UNheated building.

Always keep in mind that what works on ONE farm in ONE state will absolutely probably not work on your farm. We've proved that many times here on NAT in past yrs.