Teardrops n Tiny Travel Trailers

Hello,
I am laying out my propane line from two tanks to a heater in the cabin and the cook top and refrigerator in the galley. I planned to run it under the 2 x2 steel frame. I note there is 3 inches of clearance between the axle and the frames. I have ful sized tires and 3,500 Pd. Springs for this trailer. Adding the 1/1/2" steel angles would protect the copper tubing, but limit the spring travel substantially.
So, I am at an impasse. How do I run this main propane line safely? Drilling all the steel tubing frame for this copper line is just not feasible now with the cabin in place. if there is a sensible answer please let me know!

Gene so

RVIA standards call for black iron or copper. Our tear came with iron and with a drop under the axle, the lowest point just waiting for a rock. I redid the line with copper and drilled the aluminum frame using a right angle drill I already had. (adapters are available to do the same thing).

I would use standard plumbing techniques ( tee's, elbows, etc.) and black iron pipe with a bit of rubber wrapped around pipe and clamped directly to trailer frame....

Dale