Hey folks!  Happy New Year ~~  I solved my previous problem with the wiggly Featherlite stock bumper pull by buying a 2002 Eby 16' stock gooseneck.  Thanks for all your able assistance.  The difference between selling the Featherlite and buying the Eby was nominal, and so this was my best alternative, and I didn't have to worry about load levelors, etc.

The Eby is immaculate, but has no lining on the interior walls.  Its only 6' wide, which is fine for my four trail horse load, but I don't want to loose any more room to wall lining - so plan to go between the upright structural elements. 

Would like leads on what to line with (leaning toward 3/4" exterior grade plywood for low cost), and how to mount it so nothing pierces the exterior skin, since I cannot use the uprights to screw into (going between them as stated above).  Any ideas for fastners that would work?

Someone said Eby is a very heavy guage extruded aluminum in 2002, so perhaps I don't need lining.  I would like to hear about that, if you have any comments.

Thanks once again for your help.

If you are looking to provide a kick wall to protect the aluminum from the inside.  You might consider Rumber.  http://www.rumber.com/images/product_sheets/Rumber_livestock.pdf

It comes in both sheets and planks. Is made from recycled materials (Like Tires) so it has some energy asorbing qualities.  I've seen several brands of trailers that used the 1/4" thick sheets to line the walls of the trailer.  Or you could cut the rumber planks and place them like you were considering the wood planks.

I would think, Wood or Rumber, if you cut them to reasonible tolerances, You could place them in between the support members with some adhesive, so there would be no screws penetrating the aluminum skin.

I have a rumber sheet in my aluminum trailer but I really think you'd want to screw it in. If you go that route, be sure to drill the hole in the rumber slightly larger than the hole into the aluminum to allow for expansion of the material. Love my rumber sheets.

Thanks folks.  I decided to go with plywood, painted with black rubberized paint.  If I find out that didn't work too well, then I'll face it all with rumbar which should screw right into my 3/4" plywood...