Hello
Welcome on your first posting
Any modification to the Hollis will cause its current value
to drop considerably.
That being said, if you still insist on the modification, the rib
will have to be drilled and tapped and a special base machined.

Again, welcome
Mike

p.s.
https://www.trijicon.com/na_en/products/product1.php?id=RMR

Perhaps this would be a start
https://www.trijicon.com/na_en/products/product3.php?pid=RM57