The latest dev build (dev16629-10139) contains some changes regarding frob highlight. The full explanation is given in 5427. Most importantly, the material stages are now generated by default if they are missing. The core materials will be cleaned accordingly in near future. Also we added new syntax for customizing frob-highlight in simple cases. First of all, you can set frob-highlight with custom texture (e.g. it can be specular map) and arbitrary coefficients: fr