To reproduce: run the sample project. It ends up leaving significant blank space on the right and the bottom, whereas the normal MS Form does NOT do this and works right.

Workaround: in the Load event you can adjust the size with 10/15 px by setting the MaximumSize:

        private void Form1_Load(object sender, EventArgs e)
        {
            this.MaximumSize = new Size(this.Size.Width - 15, this.Size.Height - 10);
        }