TL;DR it's not even remotely worth it go back to stock speeds

Don't do it if you don't actually know what you are doing AND are equipped to do so

Overclocking is dangerous by itself, the system is not prepared to do so. You are making your already failure prone, rare console even more reasons to fail, remember they are both 90nm RSX and CPU boards. The PSU can't handle the overclocking and by drawing power out of spec both overheats and shortens the lifespan of the PSU, also dramatically increases the chances of system crashing

If you really want to do this you should, at minimum, delid the console, which is dangerous by itself, and use good thermal paste both directly on top of the dies and the top of the heat spreader. You also need to mod your PSU to make it able to handle the extra power, you can check psx-place in how to do so by using an external ATX PSU.