I bought a custom pair and have the universals as well. Piotr does pretty good work tuning-wise.
Agree with Kunlun in that the H8P lacks a bit of the sub-bass thump, but there's a polite bump in the lower end that's in the right region, making the CIEM sound punchy. Coming from someone that's sensitive to treble fatigue (dislike most Beyers and most Grados because of it), the H8P does it right. Exciting without being fatiguing or shrill.
They're not ruler flat, so not really for professional use. If you're looking for something slightly V-shaped that performs well across genres, give them a look. Silicone is/was a big selling point for me and CustomArt, I enjoy the warmth and flexibility it brings. I know some other people that actually prefer acrylic though, so it's not 100% guaranteed it'll be better for you.