He will turn 20 in four days. He will never be heavier than 170 lbs at best. More likely to be like Jared Spurgeon, stuck around 165 lbs. Some individual are genetically unable to add weight. Look at Aleksi Heponiemi, 5'10 and at 25 now he is stuck at 155 lbs, cannot add more and left the AHL last summer for the Swiss league. He was a two points per game in his D+1 year in the WHL, second round pick because he was so light, ans he never overcame the weakness. Lane's brother, Quinn, two years older is taller at 5'11 and weighs 170 lbs.
Caufield is a winger with decent speed, very different to be a D with limited speed. A D cannot hide.