My 410 has a drop down bunk in the aft cabin that would work for a third kid if they were small. Can’t remember if that feature continued in the 420. I weigh about 180 and tried it out of curiosity for a brief minute when I first got the boat and although it was narrow for me, it held my weight. Aside from your bridge limits, another reason you may want to go for a Sundancer is the cockpit seating. Personally, I love the sedan bridges, but they wouldn’t suit us for the way we use our boat with our 21 & 18 year olds when they come out with us. They like to bring a bunch of friends out with us for the day and we typically use all of the seating in the cockpit. The 420 cockpit is about the same as mine, but the 480 is even nicer with a lot more space. I think the difference in the LOA of the two boats is mainly behind the helm seat giving the 480 all that extra cockpit room.