First of all, you need a monitor capable of displaying a 50Hz scan rate. An NTSC TV won't do the job. If you have a 1084 series monitor from Commodore then you're in business. I tried looking for another patch by Nico Francois that would patch your system to think it was PAL upon reboot, thus allowing you're system to work in PAL mode without having to hard-wire PAL mode. It seems that it isn't on the Aminet so you'll have to make do with Degrader.
Secondly, be sure you try the Degrader method first because not all Amiga 500s have a new enough Agnus chip to switch modes. If you do have the Fat Agnus then it will be possible to do the hardware-based switch if you want to.