I noticed while playing Ivy that my barriers could still take damage during Stone Form even though Ivy should be invulnerable.
I tested it with Viscous' Cube and got the same result. (Cube was a lot easier to test with clear results)
After testing it, I can specify that there is a hole in the skybox around here. Just stand against the wall, fly straight up and when you're at the height shown you're out of bounds.
The numbers are a shot in the dark of course, but since Battle Vest gives 18% percent bullet resist, I thought 25% with an asterisk would be appropriate.