Weight distribution is a pretty preferential thing. It also depends upon the situation in my opinion. Against someone who's coming forward I keep my front foot pretty much unweighted, as my lead leg is used for checking most kicks as well as using push kicks to keep distance. When I'm coming forward, or using my hands, my weight is usually more balanced between my two feet, and when I clinch, my weight is almost always 50/50 if I'm squared up. Obviously it shifts when I want to do something, but as a start point it's 50/50.
But, that's just me, and I'm sure that others' inputs will vary.
Next fight scheduled for June 8th