Again, Iím no expert, but in order for the broms to properly support tadpoles, I would assume that they have to hold a good bit of water. Most of the pictures of pum tads that I have seen, have been of tads in the leaf wells, not the center cup. It looks like you have plenty of room to replace that large brom in the bottom with a bigger one if it turns out to be necessary. See what the pum guys have to say. Iím just going by what Iíve seen before. The viv does really look nice the way it is though. Do you know what that bottom Neo. is? Maybe it will still grow a bit.
Instead of keeping more species, why not do more with the species you keep?