I didn't have to do any of that. My iPad code is a simplified version of the sample you mentioned:
Code:
MFMailComposeViewController *myMailView = [[MFMailComposeViewController alloc] init];
[myMailView setMessageBody:[self makeCopyString] isHTML:NO];
myMailView.mailComposeDelegate = self;
[self presentModalViewController:myMailView animated:YES];
[myMailView release];
I never had to mess with what you mentioned, and I get a full screen mail composer.