Well, before I go test to see how to do it - let's see if I can guess at it.
Isn't there a Window State property for the child form? Set it to Maximized in design time. Or during runtime enter this line of code:
'Maximize the form before displaying it.
Form.WindowState = vbMaximized
If that doesn't work, then I'll go play with it.
-- and in my previous post I wasn't trying to help ya. I'm trying to figure out what the heck you're doing. (I don't use Outlook - I use my home grown program