I used 3-11/2 inch foam, no matter how I installed them they do not fit correctly when turning the bars. But they do stay in place even though they are compressed at some point. I finally left them with the wider area toward the rear of the bike and they seem to fit the best that way. Don't really know which way is correct.:shrug:
The big end go toward the seat. Just stuff them up in there from the bottom and move them around till they straighten out and fall into the area they are designed to be. I can see mine when riding just below the top of the triple tree. Mine have been in for almost 2 years and haven't fallen out or get in the way of the cables when turning. They do compress when turning and you can see daylight then until you straighten out.