I think our concensus has been that once the ball is released by the thrower, the opponent can reach across the OOB plane and if possible catch the inbounds pass.
Here is rule 9-2-11
The opponent(s) of the thrower shall not have any part of his/her person through the inbounds side of the throw-in boundary-line until the ball has been released on a throw-in pass.
I think you did it correctly. He who hesitates, often is correct.
