For what it's worth, a friend of mine borrowed a cart to use outside when her grey's hindquarters were paralyzed. I think they used it only to take her for walks, not as a full time thing, but she said it helped her hound's spirits immensely to be mobile and also aided overall muscle tone, both very important benefits. Perhaps Brian would be amenable to a similar approach. In the meantime, hugs to Alan and both of you.