I set mine to 25% reduction and all is well. It does increase effort, but also shortens the throws. I don't think you could have installed it incorrectly. It really only fits one way.
A few things:
1 - You will probably get used to it. I don't even recall what it felt like to shift previously. But for a few days after install, it was all very noticeable.
2 - A heavier shift knob will reduce the effort. I bought a cheap, heavy knob as a tester and with it installed, I can shift with two fingers as the weight does all of the work.
3 - You might need to re-calibrate the shift cable. There is a thread somewhere in here that details how to basically reset the cable by putting the shifter into fourth gear while you have a clamp released on the shift cable, and then re-clamping it. If I have time I'll see if I can find it. I have never done it because everything seems fine for me. But there are some users who did need to "reset" things once this or other shift mods were installed. That might be the case here.
EDIT - Found it. Long thread and the first post no longer has the pictures. But reading through it will show you how to adjust the shift cable.
http://www.fiestastforum.com/forum/...-Vehicles-With-6-Speed-Manual-Transmission-B6