Have never really thought too much about my backlift before as the bat tends to come down straight. However, I'm doing my Level 2 at the moment, and need to be able to demonstrate the model technique. Has made me realise that I tend to have a very open face in backlift.
In terms of sticking the bat between the legs or behind the back foot, that really is down to whatever feels comfortable. There isn't necessarily a right and wrong. The key is to have the bat in line at the top of the backswing, as then you've got a good chance that it can come down straight. Think Shiv Chanderpaul - all sorts of movement but by the time he gets to the top of his backswing everything is nicely in line and he's pretty orthodox. Or look at Jim Furyk in golf - ugly looking backswing, but just before and just after contact he is technically perfect.