Hey @methusalah999
Unity provided a full answer to the #SRPLife here , you may already know but making “exotic” shaders in HDRP should be simplier in a (I hope) near future 
Maybe it will help for future iterations of Hair Studio for HDRP.
“What we have designed, though, is the ability to extend HDRP to implement custom lighting models by creating new forward materials, effectively allowing you to author entirely new BRDFs. This method ensures that these BRDFs will support all lighting types in a coherent manner. This functionality will be provided in the 2021 product cycle.”