Bag the frags, wrap everything in newspaper, put the heatpacks between the styro wall and the newspaper, you wouldn't want the heatpacks to touch the plastic bag, they get really hot and could damage the bag or cook the frags. I have also seen people tape the heatpacks to the top of the styro.
Depending on how cold the area is that you are shipping to, you might want to wait until the weather is at least in the 40-50's, that is JMO though.
could you just use a cardboard box and insulate it with newspaper or is it really reccomended that you use styrofoam box?
do you have to use styrofoam and a cardboard box or can you just ship in styrofoam box?
You got to be carefull with those heat packs..I always shipped frags in good weather and NEVER had a problem, ever. A few years ago I thought I'd try something different and ship a bunch in cold weather. It cost me 90.00 for shipping plus the frags...lost everything.