New to building furniture (not new to finishing work), and my first
project is a utility table for the woodshop. I'm overbuilding the hell
out of this thing because I want a "practice" project that I can
actually use.

Rather than use plywood for the tabletop, I glued-up some 4/4 pine so I
could practice glue-ups.

Now, mind you, this is a *first* project, so I used the cheapest wood I
could get...construction pine. Knotty as hell to be sure. But I have
a planer and jointer, so I dressed and four-squared the lumber quite
well. Or so I tought.

I had the lumber acclimatizing in my shop for about three weeks. I
first rough-dimensioned it, then let that sit for another 3 - 4 days in
case it moved again. Finally, I four-squared it to its final
dimensions and glued it up.

Only to find that, after gluing-it up to near perfection (straight,
flat, I was damn proud!), ONE of the four boards has cupped AGAIN and
warped the tabletop.

Granted, I'm using crappy plainsawn knotty pine, but is that my only
mistake here?

Thanks for any help!