Read in another thread about "square wave" boluses. My son's Ping does not have that option, but another poster wrote that you can do it with a Ping by doing a combo bolus and making 100% of it extended. In what cases do you use this kind of bolus? I am very timid and still inept at using the combo bolus for things such as pizza--have yet to find the right formula for how much to give up front and how long to extend. Square wave sounds even more intimidating to me--but I'd like to know what it is!