I have a 2014 Sportster Forty Eight and a toy hauler. The ramp on the toy hauler is not only steep but is at such an angle, and the forty eight sits so low, that the bike high centers long before I can get into the trailer. I searched around for an inexpensive solution and didn't really like what I found so I built a simple ramp extension from some scrap wood I had. This is version 1. I will most likely redo it down the road but you get the idea. I used a calculator I found online to determine how long the ramp needed to be for the bike to clear.

http://www.discountramps.com/motorcyclerampcalc.aspx

That should work. Then I just measured my existing ramp to know how long my extension needed to be. I added a couple of handles to make it easier to carry and as a place to hook straps too - you can find them at any hardware store. I don't mind the size and weight because I have a rack on the front of my trailer that this will fit in no problem. My ramp measures 26x38 inches on top. It's about a foot tall. I painted the top with black paint mixed with sand (clean sand, if it has a lot of dirt it will clump up the paint) I don't think I will have any issues with traction.

You will probably notice the frame portion (especially at the back) is not at all straight. A buddy of mine and I built it in the dark, seems like some alcohol was involved.