Eric- I have rocked my 350lbish 2x3 cast surface plate up and onto 2 of the 3 pads when cold setting a built frame's main triangle before. Took a 1" bar bell shaft about 4 feet long. What amazed me was that the frame tubing took all that and never showed any ripples. The surface plate is now bolted to a stand that adds about 100lb and a larger footprint. Still I nudged it around a bit, but no longer any rocking
smontanaro- If you suspected the table top was flexing a steel plate pad (there's that word again) could be added. Do you know any local machinist type people? For someone with a lathe making a post is quite easy. For your needs common grade steel is all that would be needed. If there's a used tool shop (ours is a non profit for a senior center) it can be a good place to network from. There's a local model/craft store near me and the RC model guys can often be a good source for others who take on evening work. Even if the table top works out well you've got to do something about the lacking vise mount
A solid vise is one of the first 10 tools I would have.
Off for a ride than prep the clay pot turkey breast w/ mashed potato... hope your dinners are good too. Andy