No Aluminum?  Got something against quality trailers? 

I bought my aluminum Hillsboro used.  It is a 1985 and with the exception of dents in the side from the previous owners horses, it is in excellent shape.  Center gate and end gate are all working, built with angel iron frame.

Rhino liner will work if applied properly, i.e. take the undercoating off so it can adhere to the metal.  Not a do it yourself job for a long lasting adhesion.