My $0.02: Brew 1/2 of the BW with ONLY bacteria, keeping the wort hot (100* or so) until its done fermenting, brew the other half with only yeast, then blend to taste. I've found the gravity to be very stable post-blending, but you can use heavier bottles if you're concerned about that. I've never used the premade "blends" because I've read a lot of people have trouble with them. I just get the lacto from base grain. It's super easy, super cheap, and super fast.