K8200 simple Z axis improvement - gain advantage of trapezoidal rod by deleting free play of the nut on the threaded rod

Hi to all!

It's my first thing uploaded there. I did it becauce I've face print quality issue. I found (as many of K8200 owners) that Z axis is weak. I doesn't move smootly and precise because of free play. Some people fix it by adding second leading rod or replacing threaded rod by trapezoidal rod. I found cheaper and faster solution.

Nut and thread on the rod have some free play. Gravity force on the Z arm cancel it... but not enought when Z arm moving. I just add second M8 nut above s