Sub dialog form not maximized

Hi there,

I’ve built a sub dialog form which pop up as soon as the main form is displayed. I want the main form to be maximized when I publish it but the sub dialog form has to keep the size I set on design.
I have been trying to setup the form as Do Not allow Resize, Size Type Specified and everything I found on the settings in order to keep it small as I want.
As you can imagine I failed.
Could you please help me with that.

Thanks