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Thank you for the Instructable - nicely done!
I think you could probably use a piece of thin sheet metal instead of thicker plate for the slider. The sheet metal could then be brazed into the slot of the screw head. Alternatively, you could also use, instead of a flat metal slider, a length of small dia. steel rod, e.g. 1/16" welding rod. Weld the screw to one end of the rod and use a removable clamp, e.g. small set collar, on the other end. Filing or drilling a small notch/hole in the sheet metal pieces where their edges meet would allow the rod to be passed through to the bottom half of the clamp. The small hole could easily be welded closed after tacking the sheet metal pieces together.
I'd try a lead fishing sinker or wrap a few turns of lead solder around the end of the flexible tubing. The lead could be coated with some Plasti-Dip (TM) if desired.
How to make log ends perfectly flat & parallel