As a general proposition, that stuff does work. I've been using pipe insulation, essentially the same stuff, inserted into plastic plumbing unions as the feet on my PL-560. What I'm discovering is that, over time, the foam is permanently compressed by the weight of the turntable. I'm sure that, if I let it, the foam would compress until the turntable bottomed out on the turntable base (in your case) or the unions (in mine).
Still, as I said, it works. In the 6 or so months since I began using the insulation, I've had to replace it twice (2nd time was just yesterday) so I've been getting maybe three months out of each set of feet.
A trick for cutting it: Wrap the "noodle" in masking tape with the edge of the tape at the point where you want to make your cut. Then, using one of those snap-off utility knives with the blade extended several inches, place the blade on your cut line and apply light pressure. Then, with your free hand, spin the noodle while keeping your blade "plumb". Works just fine.
For my next trick I think I'm going to insert handballs, maybe half handballs, into the plumbing unions. They're the same diameter as the inside of the unions. Whole balls will elevate the table more than I'd like but half balls may lose too much of their strength and resilience.
John