+25 internet points to OrangePower for explaining a very difficult topic.
for mixed leagues, i wish the usta would let ladies play as .5 rating lower. so in a 7.0 mixed league you could have:
4.0 guy with 3.5 woman (counting as a 3.0)
3.5 guy with 4.0 woman (counting as a 3.5)
3.0 guy with 4.5 woman (counting as a 4.0)
this makes all of the above pairings viable and as equal as possible.