The process that MatterControl uses utilizes YOU as the sensor. It will jog the head and ask you about where it's at. Just go through the process, you'll see what I'm talking about. It doesn't make any firmware changes so there's no harm in experimenting with it.
joecnc2006: Repetier-Host (and likely MatterControl) will not normally allow a -Z, but trust me if you send a "G0 Z-0.05", the firmware will obey it. (much to the displeasure of your build plate and nozzle...)