I've refereed about 3 games of competitive development league football this year. I'm just not convinced of the benefits of fullsize before U17s. Short side games or smaller pitches should result in more touches, and prioritise skill development. The emergence of full size pitches seems to encourage hoof-play for too many sides. Arguably a coaching, not a player problem of course.
(In capital, 13s don't have to take corners from the corner mark, but some distance closer to the goal. This should tell you all you need to know).