For the first year of owning the 21 our tug was a Volvo xc 90 V6. Our family was a bit smaller and our trips were closer to home. The xc90 is a great car and the 21 is just within the GW limit, this was fine for flat travel but going into the hills and mtns. was a slight struggle.
we added the Toyota Sequoia this year as our family is now 5 and more cabin space was needed. The added towing capacity of the sequoia is such that when towing the 21 the trailer weight is not noticed at all