I got a real cheap Barska tripod from Walmart for about $18 that works real good with my 20-60X80 mm spotter with my cheapo assemblage. I would like to use a hugely stable concrete & steel bench while shooting rodents but benches like that weigh about 300 - 400 pounds, but I would need a forklift to get it aboard & off my vehicle. A clamp on spotter stand would be a big improvement.
A lead sled loaded down with 25-pound or more bar-bell weight(s) on top of a massive concrete bench would provide stability and recoil absorption but would not be kind to nice wood stocks and scopes because the mass of lead sled & barbell would make for lots of inertia to resist recoil impulse generated by big guns like a .300 PR and the stock and scope (tiny little parts for erector tube) would be subjected to almost all recoil impulse vs. the shooters body that would provide a dynamic resistance to recoil impulse. No problems with my little .22-.250.
The lead sled provides more stability than any clamp on tripod connection at a single point assisted by balance location. Attachment using an underside rail connection or other would be a big improvement, but with single point attachment, rifle balance would be a big factor for stability.
Imagine - a nice tender, cool, medium rare roasted beef sandwich with lettuce, tomato & 1000 Island served on a checkered tablecloth with a tall frosty glass of iced tea complete with a folded napkin having correctly placed silver (eating utensils like forks).
A photo would show how the Teflon fry pan works much better than a description.
A clamp on spotter stand sounds like a good idea. I think I will make one with a budget limit of $50 & avoid the 'out of stock" situation.