3dsMax 2017 introduced the new viewport material override. SuperClayMode is a script which mimics built-in clay mode with custom matcap texture by utilizing this viewport material override feature.
This script makes a ShaderFX shader with matcap uv on the fly and assign the material as override material and turn on Rendering Setting mode. It is designed as a toggle mode. Therefore, you should make button or assign shortcut for this script.
Free to download and use.