With a FX34, I did the mod with typical poly foam since I don't have any headphone foam.
My wife thinks they are now too tinny. She does not know why I messed with her earphones. I tried adding more foam, but I blocked too much of the sound. Either there is a real art to getting the right amount of foam, or there is a real difference between typical poly foam and headphone foam. Has anyone used both types of foam?
I have another FX34, and might try the paper clip method.
These things are so cheap now on ebay, I ordered a FX33 to hear for myself if there is a difference, and why so many people complain about unmodded FX33. To me, the unmodded FX34 sounded pretty good. The problem with the bass might depend on how far you mush them into your ear.