Minimum number of layers of foam

[Argyle]

So I re-bladed my sword. I have 4 layers on a 1/2" PVC core. In the core I have a poplar dowel. So my layers are:
Core
1/2" yoga mat
(2) layers of 1/2" blue camp foam
1/2" yoga mat

Now that it is completed the blade is pretty "squishy" but still passes safety checks. It is really wide about 4-1/2" and it leads me to wonder if I can take out one layer of blue camp foam. So that would be yoga-blue-yoga, but that might not have enough resistance.

Any thoughts?

[Gorbag]

Is this for red or blue?
Assuming blue I'd go core, blue, blue, yoga. You want a firm foam next to your core. Since yoga is squishy, the vibrations of the core are probably gonna tear it apart pretty fast. Blue isn't even the best thing to use next to your core but you don't really want to go with anything less firm than blue. The weapons Lil John has been making go blue, blue yoga.
On a red I would do the same thing but add the yoga back in on the outside so it goes blue blue yoga yoga for the same reason as above.

[Casimir Glassjaw]

Yep, Gorbag nailed it. Don't want marine foam on the core because it will shred. Blue blue marine works nice for blues.
I have been using MC 1900 instead of blue recently, it is a higher density foam that is much more durable.

[Izlakd Inedakey]

Musical chairs are in effect.