I decided to try out the Platypus Plusbottle with the pop top. Had some dividend money on my REI account, so I only paid about $10.
Here's some pics. This is with the soft bottle full at 34 oz. My Mako3 goes in and out with no problem. It doesn't deform the disc at all. The soft bottle conforms to what's around it. Tomorrow, I'll see how it works out on the course.