I cut mine too,plus replaced the old damaged fabric with leather from an old briefcase (because why not..!)
I found that hot glue works better than staples for stretching and mounting the fabric.
I didn't fill the holes,i sanded them down good,and it feels good this way (at the moment,i need a session to check)
I made a small cut with a razor for the allen key insert on top.Looks better without that gray pivotal logo
After so many years and still no company made an improved model of this seat..
After the cut it feels WAY better,like a normal seat for people with normal hands!
Here are some pics