I find that padding makes the most difference in the minimalist saddles in the hips... Where the bridge wants to pull into center to meet the tether. With the Sit N Drag, I also find it is helpful across the bottom and legs. I have Anderson which I prefer to use three or four of the "horizontal straps". I also have a home made sling (Ken Sling) that I really like and it has three horizontal straps.
Take my thoughts with a grain of salt:
My preference when I am set up with the SnD, I sit in it like a swing.
I have not sat in it more than an hour or so, never on a hunt. Just used for scouting/sitting in the woods for fresh air, practice shooting, testing my mods, platforms, tether/bridge lengths, etc.
I have played with a half dozen or more different Sit n Drag set ups playing around with them.
Others have spent more time in them in the woods. A few guys probably have 4 hour sits in one both with and without the foam. I would take their advice over mine. But thought I'd share. It's a cheap and easy mod. And if you just stitch the elastic in to hold the foam, it can always be cut out... or just send to me and I will send you a brand new sit drag...
Plus, it will provide insulation on those cold days. So if you sew in the elastic, then you have the option. Leave it out if you don't think it adds comfort. Put it in when you want a warm butt.
Good luck this season.