My rapid 7 is FAC so i have to fill quite often, i did try a bottle clamp for a bipod but it was a pain to remove every time i filled up.
Before i got a suitable QD stud (machine screw type) i just used a small back pack to rest my rifle on for longer shots, better than off hand but not as steady as a bipod.
I'd take the plunge and fit a QD stud to the S410 or have a gunsmith do it if your not confident to do it yourself.
A set of QD studs let you use a sling and a bipod which are very handy for hunting.
If your not hunting then maybe consider using a rifle rest, you can get various rests from cheap nylon bags that you fill with rice up to more expensive adjustable rests with suede bags.
Harris clone on an S410
Rapid on a cheap caldwell bag
You can just make out an adjustable metal rest with a leathr bag under this S410
I have 2 studs up front on this CZ so my sling is further away from the Harris clone.
Theres one other way, cheap as chips and won't damage your stock.
When I started bunny bashing, I used a short-extending fishing rod rest with a moulded rubber "U" on top, just stuck it into the ground - adjusted the length - and waited for Mr Coney!
Just wondering why you wanted to fit a sling to a TDR, they aren't heavy like the prosport, bipods I can understand.
The only thing I could suggest is that you use a QD attachment on the front running of the Harris or a second QD plate on the accessory rail and have a loop config that fits around the tube at the rear of the stock.
If your gun has a swivel stud, there is an item called the Stoney Point Rapid Pivot which attaches. It's available here, at a huge premium, or at Cabela's. It is clipped on and off, and is well liked by my shooting pals. Hope this helps.