This is more of an idea discussion as I was thinking about this while designing an air bearing surface at work.
If you had your table top for the lowrider, would it be beneficial to put a small perimeter on it and do a light pour of epoxy to make it perfectly level. You would need just enough to fill the lowest spots on the table.
For attaching the spoil board you would just need to drill holes through the epoxy and the table top and run screws into the bottom of the spoil board from underneath
Alternatively if you had rails on the side of the table out of C channel, you could cap the ends and then pour epoxy inside. You would still have issues with aligning the rails vertically from one side of the table to the other (you could compensate with z axis adjustment) but your roller surface would be perfectly level and smooth.
Am I out of my mind?
Again, I don’t know if I really need to do this but it’s such a cheap way of making a level and smooth surface that it’s gotta be useful for us.