Thanks for the offer to check, but don't worry about it. The video you linked said the bottles were 7oz (hopefully not 7oz between them!). I was looking over the photos of the fanny pack and I was thinking that if I bought it I would get rid of the small bottles and carry a single 1/2 liter Nalgene bottle in one of the holders, leaving the other empty. The link also says it will hold a G19, so a G26 should be no problem.
My biggest concern is the overall size. Too small and it won't hold my G26. Too big and I'll feel like I have a suitcase. I need to find the Goldilocks of waste packs. Hope this is it.