Just toss a piece of plywood in the bed when you're hauling bikes. The plywood will set up on top of the skid strips and protect the bed wood (unless you've recessed the skid strips, defeating their purpose).
To protect the bed sides from bikes, fabricate wooden rails that drop into your stake pockets and are offset about six inches inside the bed to keep the bikes off the bed sides.
This is a cheap solution you can knock together in a hour or so, it's easy to remove, easy to put in, and stores in a lot less space than a bed liner.
Since the whole idea here is to protect your paint job, attach cotton rope around the edge of the plywood where it comes in contact with the bed sides, and between the wooden rails and the tops of your bed sides.
