You really need to try and get him on the scales, if he keeps bating off the scale just gentley and calmly put him back on, and keep doing it until he settles. Don't avoid problems, tackle them head on, things normally get worse before they get better.
What distance is he coming for a chick head? I don't think I'd fly far for a chick wing, get inside your birds head, think what he's thinking.
If you let us know what stage you're at with him we can help you with next step, normally in the beginning if he's not doing what you want then he's either not hungry enough or not manned enough.
The s