I have problems in Z Axis

I am looking when ever I carve hard materials like aluminium or marble I have Issues in Z Axis bottom v wheels getting loose and spindle vibrate while carving I try many times tight and fix before job start but it will loose again I seen here Z axis stiffen but how this upgrade works can anyone give me any suggestions please.

Just for Idea I am thinking adding two T slot roller wheels in the middle of V wheels it will stronger spindle and adding bottom plate to acme rod similar like top. but It is not easy for newest users.