Frame repair question

I don’t install mainly because of the difficulty of welding underneath a car lifted only a foot off the ground. (Welding helmet is big right.)

I do allow all buyers to test fit the rails on the cars before buying and you can return purchased rails so long as they haven’t been used.

How do you guys make sure these cars don’t rust? I Rely on krown once a year, and winter stored every year, this year I plan to store it in a barn up north on a Farm. Anyone think that’s a good idea or have some other tips to make sure the car doesn’t get a spot of rust? Tell this day the car is still one solid piece and hopefully it stays that way.

Is the barn floor cement? If it is dirt or wood, then moisture will start rusting the underbody. Rodents also concern me.

Even if its rust proffed? I think it’s wood, if that’s no good guess I gotta pay 400 a month at a indoor heated storage for high end cars