Definitely something that needs to be considered!!! Switching to a lighter head increases the spine and it could possibly make your set up too stiff. That being said, it is better to be too stiff than weak so you might be able to pull it off.

By switching to the 100 grain head you will also lose a little bit of FOC which could have an impact on your arrow flight depending on where you are at right now.

Finally, while you will pick up somewhere between 5-8 fps depending on the bow you will also make your bow louder by shooting a lighter arrow.

All things to think about and personally I am one that believes if it ain't broke, you don't fix it