Got mine in Baltimore today

just watched it....its great. Already cleared up some things I was missing...
In watching (and rolling recently) I have come upto a general question. The higher belts at my school are super good at hiding their arms and keeping their elbows tight. This makes it difficult to obtain any kind of decent side control much less twister side.
Ive seen how eddie and Marcello "kill" a posting arm with a hip or knee, and some different ideas for opening the elbow, but sometimes its just not possible...
When we cant clear this near side elbow what are my options? Im thinking I have to go north south or knee on belly... thanks for any input.