Aye aye.
Yep weight. As someone who has been humping various girls about (I said "about" you bunch of pervs, you're worse than the feckin bears!) for a bit over 8 years I can honestly say that 30-35KG is the sweet spot. 40+KG is going to have you wheezing like a boiler with a couple of loose rivets, dont care how fit you are
Hope your search for you perfect girl isnt too long
K