The LWB makes all the difference with our dog, got room for her on the floor but usually now we spin the twin passenger seat round and cover the seat, our lab then sleeps on that chair out of the way.
Sleeping in the pop top is fine, come morning the dog is up and out of the seat waiting on her breakfast first thing. Sleeping downstairs in the RIB spaces becomes a bit more of a premium when the RIB is folded out but againa, if shes on the twin passenger seat then its no bother.
We're picking up our new pup next month so will need to get used to travelling with two dogs. Will be crate training the new pup so going to try getting her used to sleeping in that wee gap under front of the RIB seat when you fold it out into a bed. If that doesn't work though we still have plenty of floor space with it being a LWB for one of them while the other is on the seat.