Hi Paul
yeah I agree that it probably wont affect the performance to much but without going through all the calcs and then changing/ widening bearing spacing to compensate then it is best left as it is. remember this is being built with a pillar drill so ease of fabrication and also dimensional tolerance is less than parts made on a mil or cnc.

the binding is as a result of the lever arm of the system. the original set up was Bearing-Ballscrew-Load so the ballscrew can control the load directly. moving the ball screw back results in Ballscrew-Bearing-Load so the ball screw has to work through the bearing to contol the load and vice versa, the load is transmitted through the bearings before the ballscrew can control it. Under sudden loads this can cause the system to rotate around the bearing and as open linear bearings have clearance they could bind or cause premature wear.

Again it can be designed out but I think it will be easier to just clean the ball screw