SpiderLock rod holders. Best out there. Smooth base plate, mounted with stainless screws. On yours just drill a pilot hole before installing screws. If I was going to use a double seat setup I would spend the extra money and get the one called Dub- L- Seat. Kinda expensive compared to some but much better built, has real warranty and he is insured incase something ever happened. He also machines the center post to fit your lock in ranger base.
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Charlie Weaver USN/ENC 1965-1979