I was able to resize a FixedSingle form using the following code:

    public static void Main()
    {
        Application.Run(new Form1());
    }
   
    public class Form1 : Form
    {
        public Form1(){
            this.FormBorderStyle = FormBorderStyle.FixedSingle;
            this.Load += new EventHandler(Form1_Load);
        }
       
        public void Form1_Load(object sender, EventArgs e)
        {
            MessageBox.Show("Size is :" + this.Size);
            this.Height -= 50;
            this.Width -= 100;
            MessageBox.Show("Size is :" + this.Size);
        }
    }

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Bryan Phillips
MCSD, MCDBA, MCSE
Blog:  http://bphillips76.spaces.live.com