I used to want to play with the guitar lower, playing well is more important to me now, and because of the way I hold the pick, the tone suffers if I have it lower because of the picking angle, I'm also a thumb around the middle of the neck ish kind of guy
I have the strap set on my V to pretty much the exact same height as when I'm sat down
whatever height you decide to go with, I find most people have the pointy end in line with the top of the shoulder
if I can play something sitting down, without looking over the guitar, then I have a pretty good chance of playing it just as well standing up