It is possible to use a TID dose schedule where you give a shot every eight hours. A couple people here have done that in the 2 years I have been around. Lisa (with Cass) is one of them, maybe she can explain how/why you might do that.
Any closer than 8 hours however is not recommended. It can cause dose overlap and really mess up the timing of nadir for instance.
Prozinc usually takes about 2-3 hours before you start to see an effect on the BGs. And usually gives you a nadir around 5-7 hours after a shot. So, if you were to give a normal dose at the normal time, and then another shot 3 or 4 hours later, what could happen is that the 2nd shot starts to kick in right when the first dose is reaching peak effect. That could give you a pretty radical low number 6 or more hours into the cycle.
Tonight's cycle is very impressive actually. From 419 to 133 in 4 hours is a pretty big drop. Now if that is the low point, and you keep seeing a nadir at +4 and it looks like the insulin is worn off by +8 (if you see this in most of Chuck's cycles), then he might be a good candidate for a TID dose schedule.
If you were to do that, you wouldn't give the same dose you are giving him now. You'd take his total daily insulin dose and divide it by 3 to determine your three times a day dose.
Does that make sense?