I don't have one, but have been thinking about buying one. We have the Blvd actually and ds's shoulders are about an inch from the top harness position. I've been worried about what I'm going to do when he's finally outgrown it because he's still so little, only 32-33lbs right now.
The Regent is NOT approved for use in an airplane. I've seen pictures of one sitting next to a Marathon though and sitting side by side they are about the same height. The Marathon/DC/BV seats have a taller base (probably becaue they r/f also) and the Regent sits lower,like a bpb would. It's a really big seat from what I hear. I have yet to see one IRL (the nearest BRU is 25miles from me so I don't go there often, especially since ds isn't a baby any more!). That is one advantage to the MA/DC/BV seats though - they are airline approved and will fit in a standard airplane seat.
OK so that was wordier than it needed to be. I hope it answered your question though.
Edit to add: According to the
car seat database the MA & clones are 19.5 w x 25.5" t and the Regent is 21.5" w x 28" t. So yeah, it's quite a bit bigger.
Cheryl