You can create a simple autoexec macro for this. If you command Open Form, then maximize and set the name of the macro to autoexec, you can automatically maximize the screen when you open the application.
Yes its fine to use an autoexec macro for the startup form only.
Having said that, there might be a slight flicker doing so as the startup form (surprisingly) loads before the autoexec macro runs.
However my main point was that you can't use autoexec on the other forms which the OP also wants to maximise.