I needed to post some "finished" pictures. I got the sliders and top plates powder coated. Two step process - some sort of zinc or zinc phosphorous primer followed by a satin black textured powder coat. I really like the look at feel of it. It matches my roof rack (powder coated the same way) and blends well with the textured black plastic on the vehicle.
I used stainless hardware to bolt the plates to the sliders. Thought about painting the hardware black, but kind of like the detail. Anyways...overthinking it a bit...they're sliders.
The coating of the sliders and plates were only $60 - well worth it in my opinion. When I scratch up the bottoms, I'll touch them up with rattle can bedliner or something to duplicate that textured look (but it'll be on the bottom so who cares, right?).
No - the plates don't vibrate or make noise - they're bolted down tight.
So all in, I'm at about $650 for some really stout, quality sliders, with top plate powder coated and installed. I'm happy.
The pics: