I did a breakdown of my method for tiling textures in Zbrush over here https://polycount.com/discussion/227641/zbrush-non-square-tileable-technique#latest (tbh I meant to reply in this thread, but had too many tabs open)
Any suggestions on how to unwrap a model like this efficiently and without much stretching? Currently doing in blender but it takes a lot of time, and zbrush auto unwrap leaves too much stretch