I'm doing some more tests on my cape swatch, trying to determine what kind of risk there will be to the fabric using RTV. I cut my swatch into four little squares. One of them is taped down to the foam core, one is bordered with water based clay, the other is just free floating:
Rubber on top:
Tomorrow, I'll see how it turned out. My expectation is that the clay bordered one is the only one that will survive.