For what I know birds have an much lower superior size limit for flying forms than pterosaurs because they use two different groups of muscles to locomotion, wings for fly and legs for walk in difference with pterosaurs which the same muscles to fly and walk, this cause that the legs turn to dead weight folded under the body when birds are flying, generating flight drag and requiring more effort by the wings.
The biggest flying birds were notoriously littler than the biggest pterosaur.
Both groups were part of archosauria, they have hollow bones, air sacks and a super efficient respiratory system, so the limitations looks like are caused by the locomotion muscles distribution.
That brings me to my problem with hexpod dragons with similar characteristics to archosaurs, since the point of having a dragon is that at first glance it seems that it is a perfect combination between air and land displacement maneuverability by having six limbs one pair. dedicated to flight and two pairs to ground movement, however taking into account what they mention about the size of birds and pteoresaurs, the fact that a dragon has two pairs of limbs seems that it will make its maximum size noticeably smaller than birds bigger.
So considering that, what would be the largest size (maybe considering lenght and weight) that a dragon could reach? And in case it's really small, how could it be bigger?
For other details, these dragons will be very similar to archosaurs, without any strange material as wildcard like graphene (although I could elaborate on this in case the dragons are too small). And principally based on the body shape of this pseudosuchio, just with the wings and modifications to look like a dragon.
I ask about because in questions about realistic dragons this detail isn't enough considered