Password and button sizes

Hi Experts

I have created a form in the Forms Designer which prompts for username and password.

But which output type should I use for the password in the FormsFieldCollection? I have tried with System.Security.Securestring but that does not seem to work.

Also how do I set the width of buttons to a fixed size rather than it being autosized according to the label?

Just realized that input in the password field field of the from is output as a plain string. Can it be converted to a secure string on the fly when pressing the submit button in the form?

I know that it is possible to convert a string to secure string but I guess if it is not converted before the FormFieldsOutputData is generated the password will still appear in clear text in the JSON output (?)