Stephan Kesting posted an article by Krista Scott Dixon (Toronto, ON.) addressing the small grappling with the big. Obviously geared towards women I think this article applies to anyone who is fighting someone larger then them. This is a universal issue as many small people get frustrated when dealing with us big guys. Injury is certainly something to take into account, especially with those that do not respect the size difference. For instance I have a general rule, except for Brian my coach, that I will not crush those who weigh less than 160#. When I roll with women or anyone smaller than me I try to use technique with less use of pressure and force. This is the cardinal principle of BJJ and yet so many struggle with it. Why?
Using technique requires time to perfect said technique. We are used to using brute force in everyday life. But learning proper leverage, angles, and timing requires lots of training and drilling (You should read this as it FAILS a lot more often that not, especially in the beginning).
I caution against some of the "cheeky" techniques Krista shares such as pressure point pressing, and ripping / jonesing. Sure they will elicit certain reactions that may be favorable, but remember that no one spends all their time in advantageous positions, and when it is your opponents turn they just may choose to punish you just the same when they get you in a disadvantageous position! What is good for the goose is good for the gander!