I use a 60qt Igloo cooler for both my EHLT and mash tun. I wouldn't trade it for the world (unless I could come up with a larger one). I use John Guest fittings in the stock location and have a stainless braid hose inside. There is almost NO dead space. The only problem is that when I go to dump the grains in the dumpster, you cant roll it on the wheels as the valve or fittings will drag. The cooler holds temps very well.
Im using 3/8 inch fittings as of now but am soon placing an order for 1/2 inch.
Hope this helps