Good to hear you're pleased with your vest. I bought a similar PCM vest:
I bought the concealable vest with an extra set of cool packs. My thinking was that if I didn't want to stop for 20 minutes to recharge my packs, what were my options for swapping out packs and hitting the road? I didn't want to carry a cooler strapped to my bike. By the way, I'm waiting for a 2008 K1200GT and presently have no bike. So, I started to look for neoprene options.
Long story, short. A Case Logic ( http://www.caselogic.com/neoprene_no...?modelid=44291
) neoprene sleeve for a 15" notebook works great. The sleeve will hold the extra set of cool packs and about as much ice as you want to fill it with. I froze my extra set of packs and inserted them in the neoprene sleeve. Sandwiched between the packs I inserted 2 10"x10" Ziplock freezer bags filled with 2 cups of crushed ice in each bag. This "experiment" was conducted indoors on the kitchen counter at 70 degrees.
I wore my vest, with the first set of packs, around the house until I got bored. Coolvest claims 2 1/2 hours. From other posts on ADV I would guess it is probably accurate. What I was interested in was my storage solution for the extra pack..............................
24 hours later I opened up my computer sleeve. The ice was melted but the water was still cold. The cool packs were still in a solid state. Not completely solid but not far from it.
The sleeve works great! The 15" size works well because it allows room for the packs and ice and still gives a little room to manipulate the whole mess into irregular size storage areas in your paniers.
I think you would be ok to fill the sleeve with the packs and just dump ice over them and zip it up. I didn't check, and I don't think, the sleeve zipper would be all that water tight. That's why I used Ziplocks. Plus, the ziplocks give you clean drinking water once the ice melts. No moisture on the outside of the sleeve when I used the sandwich bags.
PS-- Last thought. I bought the concealable vest. It's cut short and will work great while in a seated position on a bike. The vest material is some sort of cotton. I'm sure it's durable but I got to thinking it might not be too friendly to the senses after wearing it day after day. No matter how well the coolvest works. I ordered a second vest. The Classic in the heavy duty nylon mesh without any packs. It was very reasonable ( cheap). I'll let you know which combo works best. If I have a bike and it's not snowing.