Because of the characteristics of CNG; you are asking question which simply cannot be answered in a public forum.

Typically the internal pressures of CNG storage vessels will range from 2900 to 3600psi and almost every jurisdiction will have very specific regulations as to how and where the vessels may be located...by example, in my jurisdiction we may have a maximum of one storage vessel on site and it must be located a minimum of 100' from any occupied structure, or it must be put in a open below grade vault that has adequate drainage so no water can collect in the vault. When mounted above grade the vessel must be mounted on a 5" thick concrete slab and there must be 6" diameter steel bollards extending 48" above grade and set in concrete 48" below grade at no more than 36" CTC on all sides of the vessel.

Just to be clear, we are talking CNG and not propane?

Propane is only around 100-200 PSI and far easier to plumb than CNG around 3,600 PSI.

It is a VERY different set of rules.

Are you sure you have CNG and not propane (also called Liquefied petroleum gas, LPG, GPL, LP Gas, liquid petroleum gas)?

My mis-statement...
Propane.

Again, my apologies, Propane.

What I have learned is in order to run the supply line through the garage it must be 'low' pressure.
Since my distance from tank to main house connection is 50 plus feet, it's not been recommended.

It looks like I'm back to burying the line..

I've also leaned that there are coated (plastic?) copper lines to help protect them.
Since I raised such a concern about putting it back under my driveway (and saw what happened to the existing line), it was suggested to sleeve the line through PVC piping.

The existing line was only 1 foot down and not back-filled properly. Basically, they just pushed the gravel back over it, thus crushing the line.

My Local Inspector requested I bury 2 feet down (ruling is 18", but I agree with her). Depending on what I hit when I dig, 2' is the minimum depth. And of course, proper back-fill.

Any other thoughts or concerns I may have over looked?