One important thing to consider here is how the table is actually
sitting. If the feet are not on a level >plane< with each other, it
can easily pull the top one way or another while it tries to settle in.
<<In this case "flat" is within 1/16". >>
If you put a level on the top when you got it, and shimmed the legs to
level and the top was within a 1/16" after that, you could easily have
this problem. Say your top is 1/16" low in one direction, then it sags
to pick up another 1/16 in the floor; now you are at 1/8". Then add a
little humidity, and you can easily pick up another 1/16". Now you are
at 3/16" in total.
But I have seen solid maple tops move 1/8" in 6 feet alone just as
humidity and heat (predicted 100 degrees here today) changes with no
If you are that concerned about the flatness on a daily basis, I would
Put the table where it will stay for your work. Secure the top as
tightly as possible to the legs, and level in place to your
satisfaction. Remove the screws from the top and replace with 1/4" lag
screws (drill out the holes that hold the top as needed). Drill enough
holes to have the screws no more than 12" apart.
Cut an assortment of shims from a hard material like really dry white
oak, from 1/16" to 1/4". Put a string line with spacer on each end (I
use dental floss for accuracy) and shim as needed before starting a new
project. Tighten down your screws as needed to secure the shims and
your top will be as flat as you want it.
Wood will react to its environment, and will move as it pleases.
Laminated wood can be more stable or less stable, depending on the
piece. But no matter what, you should never think that your table top
is a piece of granite assuming that once put in place to your
specifications it will never move.
Unless you live in a moderate climate with little fluctuation in
humidity, or your workshop is a controlled (climatized) environment I
wouldn't think of cutting into the table top because of what you are
As always, YMMV.