Not endorsing the holdback thing , but skinny at age kids usually aren't seen at elite level teams. That's just the way it is. Size does matter when it comes down to fielding a team of 20 kids. Face the reality if your kid is too small. Sorry but true.
Someone needs to tell that to some of the smaller Crush boys running cicles around our kids twice their size in the u15a bracket last weekend . Our team is from MD and they dominated us. Never underestimate a component based on size!