I like it Duck, curious to see the slide setup and all.
I really like the adj damper idea alot. The part I don't care for is the piece of bar sticking out. Cause if theres something sticking out I will run into it for sure. Aside from my preference, how cool would it be to find an old water shut off valve or a boiler valve. Put a bushing or bearing at the location where you have the sawtooth rod exiting the tank. Weld up a threaded rod to the valve handle, a nut with a set screw just inside the tank. At the plate you could have a nut welded in place on the damper.
Ending up with a crank on the handle> spins the threaded rod> in turn sliding the adj plate. I come up with some crazy ideas sometimes and most of the time they are labor intensive. The bad part is that also most of the time I get busy and run out of time and never get to try them. One of these days or years I will have time, I hope.