Dave--

The numbers work out to 50% more recoil for the 577 with an 11.5 pnd rifle and 104 ftpnds of recoil.

Betcha if you were carrying that 11 pounder and "the feces hit the fan" you wouldn't even remember the recoil!!
All you would remember would be the massive Ele trumpeting and charging you to turn you into toe jam.

But Contrare to hunting- shooting a lightweight 577 for regulation and sights would be quite memorable and painful.

I would certainly agree that a 500 NE would be the better practical pick at that weight.