Interesting. Not sure with a foam core how that works, unless he adds bb's and no foam??
This is from an old post that Ron wrote.
The one and only disadvantage I've come across so far using this mentod is the inability to add an effective rattle. The modification will render lures with stock rattles, rattleless (if that's a word?) In any case, In my opinion, it's not a bad price to pay for the added benefits.