I'm not convinced by this logic. A larger aircraft might be easier to build - more space to work in. It must be down to the design of the kit package and supervision. Presumably all the composite stuff was delivered factory built.
But there is an elephant in the room. Obesity is becoming a VERY serious issue in the UK and I believe it is worse in the States. With those luxurious seats, the chances of getting the c of g up the creek must be considerable. I would have thought that strain gauges in the undercarriage struts would make a useful indication of where the c of g actually was. Maybe it happens already.