This project was made as an example solution for the problem reported on https://forums.xamarin.com/discussion/18818/custom-page-transitions-with-xamarin-forms
Please note that this project only works with pages that have NavigationPage.SetHasNavigationBar (this, false); and that it could still be improved (since there are some accesses to a static variable).
At least it works and can be an example for people looking for this on iOS :)