On my Ultra Stick 40 I used both the 40 and 60 size Dave Brown mounts. They don't line up correctly with the blind nuts that are already installed on the US's firewall but you can take the old metal mount that comes with the US and tack glue the Dave Brown mount to the back of it and use the metal mount as a guide to drill your new holes. I did this for both a K&B 65 and a Royal 46 and both worked great! Hope this helps!