On Sunday, January 6, 2019 at 10:15:39 AM UTC-8, Darryl Ramm wrote:
Yes better be differential, have the right trip point, tolerance, longevity, and some basis for knowing the thing is suitable to install in an aircraft in critical pitot plumbing... or... I know pay $125 for the Pereguine kit and spend time worrying about more important stuff.

Does anyone know why a $125 squat switch is important for a glider (other than the FAA saying so?)

I found several uncertified pitot pressure switches online, eg MDS-0, MDA111, PSF100A. They can be found for less than $20, rated for about 20 million cycles. A suitable trip point pressure is 1" H20 column, which corresponds to 39kts airspeed. Or 0.5" corresponds to 28kts.