FYI - According to Tone there were three different versions of the seat extenders. The first gen pushed the passenger seat forward 4.5", but he got a lot of complaints that it was too much. So the second gen he cut back to 2.5", but got the opposite complaint. The version he sold me was 3.5", and it's the perfect length IMHO.

So that gives you an idea of what's out there if you had to acquire one of Tone's extenders for customization. Good luck and let us know what you do!