I weigh 180 at 16 years of age and at a disadvantagous height of 6'2". As for your question, on the standing military dumbell press I use the 75 pounders with perfect form and no leg assistance. I could probably do more seated, but the standing version is far more effective, as it uses the muscles in the abdomen and lower back as stabilizers. When done standing, the military press is very much a total-body movement... Especially when you start using the really heavy weights (i.e. anything more than 100 pounds), which usually causes your form to degenerate somewhat, meaning that you'll probably push with your legs for momentum (that would be considered as, I believe, a dumbell push-press)...