For resizing I put a resize handle in the bottom right corner, drag to resize.
I can also move the HUD around by dragging the main part of it.
Hovertext size is all viewer. The object has no control over that.
Hovertext height is based on the Z axis, regardless of the rotation of the object. If you have the object rotated you can have the text overlap the object. It can be raised higher either by increasing the Z size, or by appending a bunch of newlines with spaces in between. It can be brought lower by reducing the Z size, or by dimpling the object. I use this to create pushbuttons, sliders, and joysticks with labels.