How to control custom form bounding box size

I'm making a custom form in Muse. As I add fields, each field has a bounding box that is far larger than the field itself. As I add fields the bounding box for the form has become massive, the height is now 5400 pixels high, making the web page a rediculous height. I have no access to the height and width properties of the form and the bounding box control handles are disabled.

Any suggestions on how to control the size of the bounding box for forms and form fields?

Thanks, David