Sideclips do work if they are well done. I have never hurt myself on one. I guess I keep my fingers away from them.
If they are not well done, they do nothing, just the same as a Greener third bite.
They absorb the off axis torque inherent to a SxS shotgun, where the cartridge thrust is not aligned with the lockup and more importantly the lumps.
They are redundant with a doll's head or a greener bolt but not a Purdey 3rd bite...
They would do nothing on a O/U.
I recently looked for an inventor, but could not find anything. Purdey has used them for a very long time.
Best regards,
WC-