How many heat packs should i use

I'm shipping a ball python soon and was wondering how many 40 hour heat packs i should use. The day I'm shipping the high/low temps will be 63/47 on my end. The day it arrives at its destination the high/low temps will be 60/44. It's only being shipped about 200 miles. The box size is 15x11x7 with 3/4 insulation.

I would think 1. I tend to worry about overheating with multiple heat packs.

I would agree with one. The package will only be in the elements for a very short period. Those day time temps arent to bad as well. Depending on the size of the snake maybe a 12 x 9 x 6 box would work better? Thats what size I usually use for most adults unless its a really larger female.

Overheating is def more problematic than being too cold.

Unless you are using a very large box, like to 30x16x10, just use a single heat pack, 40 hour or higher. Multiple heat packs can indeed cause death.

If I have concerns about the low temps, I will double up on insulation, rather than use multiple heat packs.