Bolting get down vise stand

[PoorOwner]

I built this stand a while ago. Finally have space to put to use
First thing is to cut conduit and it is rocking a lot
I admit the bottom is not as flat as I would like even after grinding and straightening with a big hammer. I thought shims will stop it from rocking but the base would start to lift off by the edge as I cut it. .

Will bolting down to concrete help? Sure. But by how much?
My thought is that the steel has some bounce to it, being top heavy the base works like a leaf spring.

Will the redhead wedge type anchor where you torque down to about 25 ft pounds do the job ? Will non shrinking grout take up the void between both steel and concrete?

 

[FigureItOut]

How thick is the plate and the square tube? I can't imagine that four Red Heads wouldn't stiffen that right up. Maybe loc-tite the bolts. Any movement would then just be lack of rigidity in the stand, and you'd know you'll need to replace it or build it up. If the 25 ft-lbs. doesn't flatten that bottom plate, you might need an epoxied anchor that you can really tighten down.

 

[BD1]

I would 3/8'' drop in anchors in the corners and that will straighten it out.
If you don't need it anchored try a rubber isolator pads or even a rubber old car mat.