There are few research paper on the hillside development which you can google it, this is some of those i found online.
Guideline for Hill Side Development

Class 1 - for slope of less than 15 degrees
Class 2 - for slope of 15-25 degrees
Class 3 - slope in between 25-35 degree
Class 4 - slope with > 35 degrees.

In Malaysia, class 4 hillside development is banned, class 3 is allowed with very strict monitoring from 12 departments involvements. Class 1-2 are allowed for developments.

The 42 acres of development land in D Foresta could be divided into 4 classes depending on the slope, Class 3 and 4 slopes (21 acres of them) are kept as it is as natural forest, it is important to keep it as the forest hold the rain waters and prevent landslides during the rainy seasons.

whereas the remaining 21 acres of land are class 1 (80%) and class 2 which is good for development.

DF has been a heat lately. Many people have inquired about the property.

Same as my properties at other areas.

Sign that property market is making it return?