Arlen Ness sells them I believe both ways, and so does gator bags or gator boxes.
GatorBoxes
It is pretty easy to add the extensions if you are familiar with fiberglass work.
If not it is pretty involved, but not beyond the average do it yourselfer.
If I was going to do it, I would cut off the bottoms so that you can have the extra space.
Another note, make sure your bags are fiberglass and not ABS, because there were some years that were.
And the two do not mix.
I do not know of any sites that show how to do it, but I show some fiberglass work in my build site, here in the Harley Members builds.
Softail Bagger
And like Frisco says you do need to be careful about going around corners, not as bad as you might think, but I have dragged mine at least once.
When you are doing it, check your lean angle, I used my pegs, then added about 3/4 of an inch, so that my pegs drag first to let me know that I am going to scratch the bottoms.
Although they are the bottoms that no one can see.
Streched Bag question 
I dunno, but yeah, I do like that look with the flared fender and all, maybe some more lighting in the fear of the bags!!! 
Linear Mode
