ball bearing off-center load question

I am trying to design a very cheap linear system. It's for a manually driven 13" long household device. It consists of two parallel 5/16 rods and a slide with preloaded rollers.

For rollers I use metal patio door rollers:

I am thinking about using a pair of small plain ballbearings on the same axel with the spacer between them instead of a each single door roller. The ball bearings will roll on the side of the rod since the spacer will be shorter than rod diameter.

It would be much cheaper. But I am concern about off-center load.

Is this design OK?

Thanks