On Sunday, February 18, 2018 at 12:47:54 PM UTC-6, Dave Springford wrote:

Snippage

It is much quieter than the K-21 so the noise feedback for speed control is gone.

Not an instructor but my solution is one of training. Enter the patter, gear down, side window scoop open. Instant audio airspeed. Maybe not as sensitive as an ASI, but certainly provided clues as to what you are doing.

I would assume that your club's Duo has windows with scoops on them. Try it, particularly with those who tend to wander a bit on speed.

Steve Leonard