I’ve used four jackstands as support under vehicles for years. As an example, it’s impossible to remove a manual transmission from an F150 pickup to replace the clutch unless the truck is on 6 ton jackstands set at their highest level. Otherwise the transmission can’t be removed from under the vehicle while sitting on the transmission jack.
As mentioned, once the vehicle is atop the jackstands, shake the vehicle to check for stability before going under the vehicle.
Tester