DH and I rode w/ our then 3.5 in February. It was a very tight fit - I am a little on the big side, DH is normal size. BUT, I wouldn't have let her go w/o us being able to "wedge" her in. I felt much safer. I had to sort of sit angled towards the inside, but it was fine and we had a fun ride! DD had a look of terror the whole time but when we got off she said "That was a little scary" followed by "Can we do it AGAIN?!"