I was able to get them under mine, both the stock seat and the new Mustang seat I have now. The fit was tighter with the Mustang, especially the bolt at the rear of the passenger seat, but I made it work with a little force. Do you have a sissybar attached? Have you tried loosening up the ties to lenghten the yoke?
I had the same problem when i went to a mustang seat on mine. I took a hole cutter tool that I have to make gaskets with and cut holes where the rubber cushions go and it worked great. Have my zip off bags back on and loving the ride.