Precision Piezo (http://www.precisionpiezo.co.uk) system can get very high precision bed leveling. First I tried simple way mount piezo to extruder, but my MK8 extruder is very hard to mount piezo. Because of structure, heat, etc. Then search underbed mount, but not fit to my printer. Last make this very simple underbed mount. Only sandwich between base and table. Easily change total height of mount, for fix bed structure.

I make detecting circuit myself and add one more input of piezo. (Original has three input, but I want four) Circuit (https://reprap.org/forum/read.php?1,767998,page=38) post 289. Use piezo "Murata 7BB-27-4L0". Firmware Marlin bugfix-1.1.x G29 - Unified Bed Leveling(http://marlinfw.org/docs/features/unified_bed_leveling.html).