Still not sure where the problem is? The bearing blocks can take loads in all directions, (slightly reduced where the rail is supported maybe, but thats why I put them vertical rather than on their side)

I see what you mean In your diagram but not sure how that relates to the one I've drawn, dose that use skate bearings and unsupported rail?

I could put another rail underneath like in your sketch but this will add to the cost, And in that case Id rather use linear rails as they would be the same cost as 2 supported rails but are 4 way loading and much much stronger.

If Ive made a mistake I want to known, but at the moment I dont understand......

I have thought about the wall mount option but not sure how easy it would be to use.... Im sure I remember a design that could be stored on a wall tho.