My Harris has a finger screw. Finger tight.
Clones often have a hex head. Not to tight.
IMHO and Understanding:
A sling stud and attachment should be designed to take the weight of the rifle+scope with pretty harsh handling but the pressures on the fore end from a bipod could easily exceed the strength of the attachment or fore end.
If it were me (and I do this almost every day), I'd go finger tight until the pads of the bipod doesn't allow movement. If using an Allen wrench, torque gently with the short end in your fingers until the bipod doesn't allow movement.
Basically, as I undersand it (AIUI) no tighter than needed to keep the bipod from moving fore or aft, left or right.