UIPopoverController automatically resizing to max height on pushViewController

This fixed it for me after I had the same issue (coincidently also today):

EDIT : As contentSizeForViewInPopover is deprecated in iOS7.0 so use preferredContentSize.

Original answer below:

In your detailViewController add this:

- (void)viewWillAppear:(BOOL)animated {

    CGSize size = CGSizeMake(320, 480); // size of view in popover
    self.contentSizeForViewInPopover = size;

    [super viewWillAppear:animated];

}

You also want to add something similar to your original DeviceDetailViewController to prevent resizing when tapping the back NavbarItem.