If the 70 qt is anything like the 58 qt coleman xtreme 6 I have, there is a channel coming from the middle of the floor down towards the drain, which is actually very low on the cooler wall (lower than the main part of the floor of the cooler). I use a stainless steel braid that comes right off the adapter to the SS valve, and I have almost no deadspace at all.
I was just looking at the coleman website
, and it looks like it says the 70 qt does have that drain channel.
I can vouch for the xtreme 6 coolers...hold heat very well...I'm sure the xtreme 5's do as well
EDIT: holy $h1t...so many people posting all at once!!!