i am no info on treewalker BUT i can tell you this, no way that seat is going to be comfortable sitting in it for longtime.adding chill pack seat against tree is not good.
i have back trouble ,we will all get it as we get older.i try everything in my ladderstands to get comfortable.

unless you have seat like summits have,i cant see how you are going to not be numb or stiff ...........
i sat in treewalker at sportsmans show at harrisburg.no way it was great seat and dont let anyone tell you it is.try sitting on a swing with that seat.it will pull in on your sides.
at 18 ,yes thats great seat but older,i would not rec it even tho i have not sat in it for 8 hrs.
sitting in it for 10 minutes at show was enough.