The Remington 11 is the basic Auto-5 design but does not have the shell cutoff on the receiver. They even interchange some parts. It is my understanding that Mr. Browning licensed his design to Remington so it could be built in the States after some sort of conflict between Browning and Winchester over royalties.
I have an old Police Model 11 dating from the 20's. I tracked down some new springs and a buffer and it works perfectly with full-power loads. On the "light" setting it is about 95% with lighter loads.
While it's a really fun and reliable gun, it is a heavy sob. If you like the Browning long-recoil design but wanted something a little newer, lighter, and (probably) easier to find parts for, you might want to look for a used Franchi 48AL. It's a knock-off of the A5 recoil system and is a proven field gun. I have a 48 Heavyweight 12ga and use it as my (really) bad weather gun.
Some say that the Browning long-recoil system "kicks" harder than other designs. I think that felt recoil is largely a matter of proper fit. Whatever the case, it's a proven system.
IMHO, if your Dad really wants an 11 I wouldn't steer him away from it, but it wouldn't be my first choice.
