I've found that Amdur sensei's version of shihonage (the one where you put their forearm on your forehead) goes along quite nicely, even with those trying to twist out of it.
Hi Mark (owe you a phone call),
Yeah, but I've seen gumbies that can even twist out of that. I can lock down several versions of shiho so that it becomes EXTREMELY risky for uke to twist out of. Locking it down isn't the problem. Hurting or risking hurting flexible beginners who don't know no better is the problem. If I lock them too tight, they no come back no more...
A little forth control pin goes a long way to understanding just one of the possibilities to assuming gumby status.