The amount of cure used is in relation to the amount of meat being cured. The time in cure is directly related to the thickness of the meat, so if they are stacked on top of each other touching that will take longer to cure. I inject my meats just to insure consistency in the meat curing process.
We have all, at some point, in the first few tries in curing have miscalculated our times, but we learn as we move forward.
Good luck on your next attempt..
Humphrey's DownEast Beast W/BBQ Guru