I think the better option is to set the custom size by programatically.
objectiveC:
- (void)viewWillLayoutSubviews{
[super viewWillLayoutSubviews];
self.view.superview.bounds = CGRectMake(0, 0, <width>, <height>);
}
Swift:
override func viewWillLayoutSubviews() {
super.viewWillLayoutSubviews()
self.view.superview?.bounds = CGRect(x: 0, y: 0, width: 300, height: 400)
}
Put this code inside Modal view controller