Shapewear making the lines WORSE

So, as evidenced in the first pics I need some shape wear with the satin dress. No way I'm spending th $50+ on Spanx, so I headed to Target for their version... which seemed reasonable enough.

ASSETS pantyhose. Sheer, smooth, right?

From afar... not too bad. (*Same night with the crummy camera situation.)

Not too bad, again. Oh, and that's my veil, by the way. :)

BUT

With good posture, the tummy line is visible...

And with bad posture it's awful!! Way to do the OPPOSITE of your job, nylons!

On a side note, they make my feet slip out of my shoes too, so I'm thinking this might be a $12 loss.

I need suggestions for another (affordable) attempt at shapewear!! Are just control top nylons sufficient??