[Witchdoctor]

Instead of sloted holes what if the arch slid in a groove to eliminate fixed positioning laterally.

The arch slides this way across the top but not along the sides of the table.

I am sure this would create weakness if it were slotted the whole way.
A rail system would probably have to be incorperated. I could draw this but I am sure you have engineers that could do it in better detail than myself with a pencil and paper.

It would have to be a U with top rerturns with a opening in the middle. The edge of the table could be solid and may need reenforced to accomidate a tightening mechanism from the bridge itself.

Hope you can picture what I am talking about here. This would create a slide with no limitations just like the top rail of the bridge/Arch .....