wingchun100
Senior Master
When it comes to good grappling size isn't that huge of an issue. As such, and I raised this in the "outside game" thread, learning grappling is the best path. If for some reason you don't have the time or inclination to do so I can only think of one thing. Find a grappler who is willing to spar with you on a regular basis and with them practice and work out what works best to keep them outside of their "sweet spot" until you create an opportunity to escape the situation entirely.
Oh no, you said the dreaded "S.S." phrase again! LOL