| Here's what you need to know to figure out what you want to do.
Know your insulin units:grams of carb and insulin units:blood sugar adjustment ratios, and decide on what your diet is going to be like, and you also need to be comfortable with how your body typically handles Humalog. Probably easiest for me to explain this all is to use my own handling of things. You'll also need to know your BGL before shooting up and what your target BGL is going to be.
Once I get to lunchtime, my insulin:carb ration is 1:10. For bolus corrections, I can expect 1u of Novolog to drop me 35 mg/dl. Now let's say my BGL is 100 mg/dl testing before lunch, and I'm going to have a meal with 40g of carbs. That's 4u of Novolog to get me back to 100 mg/dl if that's my target number.
If I were to inject the 4u of Novolog, I am pretty confident that 70% of it will have been used 2 hours after the injection. 70% of 4u is 2.8, so 2 hours after the shot I would have 1.2u of Novolog remaining. Approximately. Still, if I've eaten something reasonable without too much fat along with the carbs, I can be reasonably confident that when I test at 2 hours after the shot that any insulin remaining from the bolus will be working just like a correction bolus. So 1.2 * 35 = 42 mg/dl. 2 hours after that shot and eating that meal, I would expect to be around 142 mg/dl.
But hopefully to help you understand what's going on, imagine if I'd selected 65 mg/dl to be my target after that premeal test of 100 mg/dl. So instead of 4u, I would have shot up with 5u to get the 35 mg/dl of correction from 1u additional. If I had done that, at the 2 hour mark after the lunch bolus, I would expect my blood sugar to be around 117 mg/dl, since 70% of 5u is 3.5u which means 1.5u remaining. 1.5 * 35 = 52.5 mg/dl of action left to go, and adding that to my target of 65 mg/dl gives me the 117 mg/dl.
I hope that helps some. I don't know if I really explained it well, it's something I don't have to think about too much now that I've become accustomed to it.
But if you look at that, you might see that the way to potentially get the numbers lower 2 hours after a meal is to bolus some extra insulin, do your test 2 hours after and then from there work out how much of a snack you may need to keep from dropping low. But you should only go mucking around with overbolusing if you are confident that you'll be in a good position to take care of yourself in case of hypoing and only if you are confident with your numbers, ratios, and typical insulin uptake profile.
I'll often do overbolusing when I'm at work and know I can safely have snacks during the afternoon. | 
