Mike,
My experience with the Duo mount was unpleasant. I had one mounted on my 7X30 Waters and at less than 100 rounds I found the rings and base loose. All screws were originally tight. I do not use locktight on scope mounting screws. This is a personal preference.
The 7X30 kicks less than a SRH 454 that I have shot, so I can imagine what could happen.
I replaced the Duo mount with a Refield 3-ring Magnum mount. I have used the Redfield mount on other guns and have had great luck with these.
Rick