you might need cooling packs not heat packs, ours come with a cool pack. Make sure all bags fit tightly, if you have extra space, fill bags without fish/inverts so the fish/invert bags don't move around much.
swf.com "We use high-priced bag clipping machines to ensure that the oxygenated bags you receive retain the oxygen that was placed in them at time of shipping. Each item is packed with its own requirements and specifications based on experience from years of shipping live goods overnight. Each order is then placed inside a thick styrofoam cooler that insulates the contents from any damage or extreme temperatures. This secure box is then placed into a corrugated box that further secures the safety of your new purchase. [...] Destination temperatures for each individual package are determined daily and Cool Packs or Heat Packs are included for free when necessary."
Our inverts were package at 2:48, picked up at 3:21, and delivered 9:33am the next day.