Be sure to take a look on ebay for folding wheelchair ramps...greater weight capacity AND often less $$.
I'm also a bit concerned about the width of the dog ramps...even if they weren't injured, I would think that stepping off the side just once would sour them on ramps for good.
Keith made a great ramp using a ramp kit from Home Depot (two heavy duty metal braces that are screwed onto tw0 2x8 planks for loading quads and ATVs and such). He then attached a 3'x6' piece of plywood and laid down no-skid tape on that. It works beautifully, but is too heavy for me to lift
I needed the help of Liz (Nootka) and Hillary or the Crabby Chicken family to get it down from and back up on our luggage rack! It's longer than it needs to be, so I'm hoping we can cut it to 4-5' and lighten it up a bit. We could also have used lighter plywood than we did, since the 2x8s bear the weight, but I was paranoid...