agree re rainbow, I like it, honestly, I feel like it's huge when I'm inside it, excellent headroom, hard to even consider it an ultralight tent it's so big inside. If you order a new one make sure to get a middle/center back wall guyline connector, I believe Henry will add that if you ask him to, it's worth it, in heavy winds if you are camped with the wall facing the winds, it can use a bit of support on that big panel.
But this tent is very large. I share others concerns with dog claws on a thin silnylon floor but that would be the same in any of these shelters that have floors so that's not related to rainbow specifically. A 1/8 pad might be useful to avoid issues, that's only about 4oz, and you can make the dog carry it.
I don't think I'd want to be in this tent in real rain with two people though, unless you both can squeeze together onto the 36" or whatever floor width it has.