Linear Bearing Aspect Ratio

[CubeSeventy]

I have a system riding on 4 linear bearings, 2 bearing per rail. The rails are approximately 6 inches apart. The space constraints on the system allow me to only be able to actuate motion along one rail or the other, doesn’t matter which. I'm wondering if there are any relationships or rules of thumb that would help me determine an optimal or minimum distance between the bearings on each rail to prevent binding or any unwanted hysteresis?

Thanks

 

[sreid]

An old rule of thumb was twice along as it is wide minimum.