OK, so I'm way late on this thread but I'll toss the following in here now.
At the time you guys started this thread, I didn't really have anything in mind. But, the closer I got to trying to set up to flatten the hunk of Michigan chocolate the Ambassador brought down here in March, the more I realized I had to do some preparation - more than I thought. The big problem was my work table/bench system. Ten years ago when I built it, I put together some interconnected tables using MDF. It was rock solid and dead flat - for many years. However, age and a lot of work caused sags here and there.
Here's the original layout:
I approached the updates from two directions: a REAL work bench and firming up my router table as a stand-alone.
For the work bench, I started with a 96" x 30" x 1.75" laminated maple bench top made in Michigan and sold through HF. I added legs for each end with steel units from Amazon. For the center support, I made a single leg with PVC pipe. All legs have levelers in the bottoms.
To firm up the router table, I removed the fence, then flipped it on its top. I removed the MDF legs and apron, replacing them with plain old pine lumber. I jointed some pieces of 2x4, glued them together, then jointed and planed them to 3 1/8" by 2 5/8" to make new legs. Pine 1x4's were used for the new apron and stretchers. The resulting assembly is dead flat and large enough to support the cage for flattening the slab, which I started on this afternoon.