Initialize WinForm of small size

I have a borderless WinForm which I initialize to Size(20,20) in the designer.

Even though I can resize that form programmatically after it initializes to as low as Size(1,1) (I do that using MouseMove events), when it first initializes its Size is roughly (100,40), instead of (20,20) which I set on the designer.

How can I initialize a borderless WinForm to any Size I want ? Is there a property I need to tweak which I am not aware of ?