Hey Eric, so, in another life, I worked
as a grip, and gaffer on various indie films and series, so, I've done a bunch of rigging and grip stuff.
Here's what I use to attach to my rack on my rails.
I use the SmallRig SuperClamp on my cargo basket's thick tubing. There's others like it that are decent as well.
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SmalRig Clamp Mount with 1/4" Screw Ball Head Mount 1124 comes with a clamp at the bottom and a 1/4" screw on the top. It can mount monitor and LED Lights on the one end via 1/4" screw, and it can lock the rod of 15mm-54mm on the cage via the clamp tightened by the locking knob.
www.smallrig.com
I use Smatree's and SmallRig's Action Cam to 1/4" adapter, and entirely replace the "bottom" half of the action cam mount with it. Smatree's comes with a really nice wrench.They're both solid metal. I really like the Smatree one, with its rubberized bottom.
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I screw that directly into the SmallRig mount above, or I use one of SmallRig's Magic Arms, which will mount to either a hot shoe, or for what you'd need, you can unscrew the hot shoe mount and screw it into the 1/4" above. They come in different sizes, all the way up to 11"
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SmallRig 11 inch Articulating Arm 2066 is equipped with 1/4’’ screws on both ends respectively. It features an ergonomic wingnut for great convenience that could help to adjust any angles based on your needs.
www.smallrig.com
ALL of those above are metal, and lock solidly.
And when I do suction in crazy places, I use this beast. Yep, it's massive - big enough for a full sized DSLR, which is why I use it along with the other mounts.
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I've got a couple hundred pounds of other mounts, clamps, extensions, etc... but those are my favorites, which should work well for you.
When I do run magnetic, if it's close to the car, I use this and a safety cord. It takes a bunch of effort to pull it off the car - may be suitable for quick stuff NOT in a tornado, lol!