We have Ford Kuga which has a smaller boot than your Xtrail, we also carry a mobility scooter in the boot (which we strap down) We have installed a dog guard (there is a company in Tamworth, which manufacture the dog guards for Ford/Nissan etc on ebay for about £100) that way we load the boot right up plus in the event of an accident prevents the content of the boot including the scooter into the cabin space.
We have also brought a protective cradle on the back seat it is like a hammock connected to the front and rear headrest, it has slots through the waterproof/dirt fabric to connect the dog harness, plus it keeps your rear seat clean and dry.
Unfortunately I have suffered a brain injury and occasionally I get confused and often say the wrong thing.