Don’t cook in cryovac, unless it is rated for sous vide. The seams are frequently not up to the sustained warm temps of sous vide.
You never cook to weight. You cook to thickness of the thinnest dimension, and amount of collagen breakdown you need. For steaks and tender cuts, it’s entirely determined by the thickness of the steak. For parts of animals that actually work (the front, the back and the bottom) it’s more about collagen breakdown than thickness. As such, for steaks, format makes more difference than weight.
I trust the advice of Anova, Nomiku and other manufacturers of sous vide gear about as far as I can throw them. Doug Baldwin has your safety in mind.
http://www.douglasbaldwin.com/sous-vide.html