Yes something like that. Slide throttles are difficult to make because they
tend to stick when there is a large pressure differential across them.
some sort of ball bearings are essential. I have never taken an Ellison
apart however to see how they do it. They may not consider this a problem
in an aircraft application. A few  race car drivers were killed
in Europe because of sticking slide throttles. I am not taking any chances.
Perhaps one difference is an aircraft throttle is controlled by a push
pull cable while race cars typically used a pull cable and a spring
in the old days.

Paul Lamar

I would do it like a linear bearing; put  V grooves on the plate and body surfaces, balls in the grooves, flat plates of delrin with holes as bearing cages (bad form to suck a ball bearing down the intake). Would need to test under a major source of vacuum or pressure for friction and leakage.
...Chrissi

Linear bearings were my first thought.
Linear bearings don't look so good when you make a scale drawing.
Try it and upload it here. A little four wheel car like I show is much
easier to make. The ball  bearing cam followers are about $7 each from
McMaster Carr.

Paul Lamar
 
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