How can I tune the bounding box size and the initial height of the camera?
In the Prepare->New scan menu, you can specify a config file. This is aimed at advanced users who want to configure Skanect is a more precise way. It follows the .ini file format, and it can be used to adjust the initial camera height, for example to start a full body scan with the face of the subject. Here is an example of config.ini file that sets the initial position at 80% of the bounding box height:
[BoundingBox]
center-y-as-height-percent = 0.8
center-y-as-height-percent = 0.8
This can be combined with the Height x 2 option for the Aspect Ratio setting. You can also specify the bounding box size, here is an example that also sets an optimized size for a full body scan:
[BoundingBox]
center-y-as-height-percent = 0.8
size-x = 1.2 ; x is the width in meters
size-y = 2.2 ; y is the height in meters
size-z = 1.2 ; z is the depth in meters
center-y-as-height-percent = 0.8
size-x = 1.2 ; x is the width in meters
size-y = 2.2 ; y is the height in meters
size-z = 1.2 ; z is the depth in meters
If you need even more control on the bounding box, be sure to check this FAQ entry.