Definindo o tamanho Mínimo e Máximo do Form

procedure TForm1.WMGetMinMaxInfo(var MSG: TMessage);
begin
inherited;
with PMinMaxInfo(MSG.lparam)^ do
begin
ptMinTRackSize.X := 300;
ptMinTRackSize.Y := 150;
ptMaxTRackSize.X := 350;
ptMaxTRackSize.Y := 250;
end;
end;