For me, I'd only line-x over the rail if the thing is color matched.
If I get line-x in mine at all It will be color matched, but the $1200 price tag and the fact every installer made it dang clear they don't want to do it is why I haven't done it.
I'm so dang sick and tired of all these cookie-cutter-companies. I'm not paying someone that much when they've made it plain and clear they don't want to mess with it. If its color matched it can look pretty good. But unless your trucks black, it won't look quite right on these old trucks. But if you need it and are going to use the truck, looks can come second to having rust and dents all over the rails. The diamond plate rails will look worse than the bedliner on the rails. but they are functional.
I havent been in too big a hurry since I have my trailer, so most of the abuse goes to the trailer. I would like to be able to get heavy loads without the trailer too though. trailers are a pain in the butt sometimes.