You can add trash until the compartment is full and the compactor will not compact the trash any further. The compact cycle time will be shortened as the compartment fills up. During full cycle the ram travels 2/3 of the way down into the trash bucket.
With Humalog's short action time of 3  hours, covering postmeal highs with more insulin can be considered as soon as two hours if a meal dose have been underestimated. Of course, not as much sliding scale insulin would be needed here as before a meal, because some of the meal dose is yet to work.
From personal experience, I know that NPH peaks about 8 hours after you take it and can cause your blood sugar to drop rapidly. I also know that Humalog is very fast acting and the combination of the both at dinnertime may be causing the rapid drops.