I personally think if you are 20% body fat or higher that you should use LBM for calculations. Below 15% you can use weight, 15-20% you will have to play around with.
That's just my theory, though.
Now, with regards to leucine. Since pre-workout insulin spiking is very beneficial and can be done with carbs alone - or a high carb meal - try spiking insulin preworkout with a small meal or shake - and without the leucine - then workout, then have a scoop or two of whey PLUS leucine, post workout.
Leucine will also spike your insulin, so coming home from the gym, your insulin should still be high from the preworkout spike and to further spike insulin and stimulate protein synthesis - at least according to the literature - you can consume leucine in the postworkout window.
Actually, if your workout is less then 90 minutes and you have the preworkout shake/meal within 45-60 min of working out, you could probably ditch the leucine as part of the PWO shake and take it with your first PWO solid meal, which would be 60-90 minutes after the PWO shake.
Summary (leucine use, my rec):
This is if you don't workout to close to bed time. Otherwise, place the PWO-meal leucine dose somewhere else in the day, about 5-6 hours after you first take it in the morning.