Take a look at last year's cup finalists
NHL Teams by Weight, Height, and Age.
Teams that are
tough and
good defensively go far, not necessarily teams that are big and heavy. This is a trend that has persisted since the lock-out:
12/13 Chicago and Boston
11/12 LA and NJ
10/11 Boston and Vancouver
09/10 Chicago and Philadelphia
08/09 Pittsburgh and Detroit
07/08 Detroit and Pittsburgh
06/07 Anaheim and Ottawa
05/06 Carolina and Edmonton
Of those 16 teams, 10/16 were good defensively and tough (excluding Carolina, Edmonton, Ottawa, Pittsburgh x2 and NJ). How many were big and heavy? I don't have the numbers for height and weight unfortunately, but it looks to me like Anaheim, Philadelphia, and LA are the only teams with big, hulking players to have made it to the finals (3/16). Again, someone with the numbers should chime in, but this claim about height/weight being the most vital key to success is a fallacy.
Defence and toughness (mental, not just physical) are the only common denominators.