Was going to mention adding the second thread for tensioning but for some reason I thought that drawing was for the Y-screw...oops. I've got a thread on both ends of my router X-axis screws for the same reason.

Do you reckon the D2812215 Belleville washers would be suitable for preloading RM1204 ballnuts? The screw I have here is actually 11.60mm diameter so it's going to close... Apparently 10-15% of static thrust rating is a good compromise for preload, so 1KN. I probably need a lower spring constant for that as such a small deflection will be hard to measure.