Hi Kiraze,
I don't know what powernet is like, but these ones are made of crystal lycra. They seem pretty firm, and it held in my middle quite nicely, but I don't know how they'll go over time - whether they'll lose elasticity like a favourite swimsuit! They do have seams up the sides, if that makes a difference...
If you're any good at sewing or know a seamstress, I found
another seller who sells lengths of powernet (and black mesh leotards), so that is always another option...?