How big does a stags horn sumach get?

5mtrs high 6mtrs spread. I would only cut it back, prune it for shape. Take off over hanging branches etc.

These trees do sucker i.e. grow from their roots. As a kid my parents had one, it keept growing through the lawn. I had one at a previous house and the suckers pushed up through the concrete.

Ours has not suckered seriously yet. Only right close to the original trunk. I think I read that if you lop or prune it encourages suckering.

They dont seem to be quick growers -not in my garden anyway. I've aquired a few new ones from suckers- theones I don't want I just cut off. I've cut mine back at various times without problems.