If you really want to mix levers/mechs that have different cable pulls then you can with the appropriate jtek shiftmate.
http://jtekengineering.com/shiftmate.php
@Greenbank started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
If you really want to mix levers/mechs that have different cable pulls then you can with the appropriate jtek shiftmate.
http://jtekengineering.com/shiftmate.php