Here's a compilation of updated Mantra Shaders. I've left the HDA unlocked so you can root around inside. These are not bullet proof. So understand, if you use them, and they break, you'll have to dig around yourself.
Technically similar to the one's I've done before, but now I've swapped crazy matrix maths for the sample sphere VEX, which makes it a bit more consistent, and easier to modify.
Also, when you increase Pixel samples in the Mantra ROP, you can lower the shader samples.