after he tied with you is NOT the time to learn that he swells up much bigger then you ever dreamed, and much bigger then you thought could be possible or can comfortably take .... at which point you learn the hard and painfull way, that some dogs can be serious hung, make you feel like you might pop from the knot, and all you can do is whine like a virgin bitch and pray he does not last 30mins or more.
Dogs do not get hard until they all in ... many are surprised to learn that one the first time. His dick not that big, i take dildos bigger then that ... but you need to know how big the knot is.
Can you handle a knot the size of your fist, or a baseball, is the better question.
Can you handle full hard length, is a better question, lot of women have issues with length.
Jack him off first, and check out the equipment before you get a surprise you can't handle.
Dogs are no different then men, you might know 12 all similar size range, 13 might be the mutant with the actual 10 inch beer can.
Knots are the outlier i have seen, same breed, same size weight of dog, same size sheath, and hard, same range thick, but in 10 dogs same breed one had a knot barely bigger then his dick, and one was good bit bigger knot, one was scary huge knot, not quite the hot dog on a baseball comparison, but damn it was not far from that type size difference.