Hi Andy,
I keep all the intact ram lambs (once weaned) with the tups. There are 16 together at the moment.
I've never had a problem, although new additions do get "checked out" by the older tups, with a bit of head banging to make sure they know their place. It's more of a ritual however, and after ten or fifteen minutes they are all grazing together.
Just keep an eye on them for a while, to see that he settles.
John