I double under pass a lot and have never had this done to me.
This is likely because the first rule about defending double under passes we have ingrained into us at my school is to immediately underhook their arms back. From there, there are several offensive option.
First time I heard it called this but anyway my favorite move from this position is to:
underhook an arm, gable grip the underhooked arm its now suprisingly easy to rip the arm out and finish with th triangle.
as for the shoulder crank mentioned in the first post I'm having trouble visualizing it can you get a pic?
Rodrigo medeiros had a seminar discussing several options from that position. And that was some time ago.
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