If you were doing it over, would you just go with the Kerk screws and VHD nuts or use ball screws again?
The Chinese ball screw guys do offer double ball nuts (zero backlash), did you consider these at all?

Do you remember what they charged you to machine the ends?

Machined end lead screws and VHD nuts from Kerk are about $850

Chinese ball screws are much cheaper depending on the machining cost.

How did you make your wipers and are they working good?

I am stuck on my design a bit until I figure out what to do with the screws and nuts...