Screen centre for forms

I've the following problem with my MDI child windows

If i set the property position of the child forms to poSCreenCenter then
the form isn't centered.
I've made a main form as followed

Main menu
Panel for speed buttons

The clientHeight of the form shout be

Form height minus the height of the MainMenu, Panel and statusbar

My screen resolution is 800 x 600
the client height is 562 it should be  the height of the Panel and
Statusbar smaller. Is there a solution for my problem.
Please sen this also to my email adress