How do you keep fish warm when shipping?

[Alfred]

I am going to be shipping some fish for the first time and ran a few tests over the last few days.
My box is 8" x8" x 15" high, I cut 1/2 foam to line the inside of box.
The bag with water and oxygen fits easily with a few loose peanuts around it.
I cut a 1 inch square hole in the top of the box and tape a ultimate warmer on the other side of the hole.
I ran a digital thermometer into the bag and taped up the box.
I did this around 4 p.m. and checked it every few hours and by bedtime the temp was down to 82. At 8 am the temp was 79.
I plan on shipping overnight with am delivery.

Should I be doing anything different?
I'm worried of the loss of temp from 86 - 78 over night in 70 degree weather.
I thought maybe I should use 2 heat packs or is this acceptable temp loss.
Also what do you do in winter shipping?

[poconogal]

When I received Discus via Fed Ex in March, the shipper had 2 heatpacks in the styro box. When I've gotten fish in the winter, he puts 3 heatpacks in. Also, wrap each bag in a layer of newspaper. Usually 3 bags are used per fish when shipped to me.

[mmorris]

If I remember correctly Jack (Discus KC) used four heat packs when he shipped fish to me last winter. Heat packs aren't cheap but it's not something to cut corners on.