The schooner looks stable, I hope, thereby getting any pressure points in the mattress.
The knobs are designed to prevent slipping - but this does not work in a manual movement of the mattress (eg sheet change), since you have the location of the schooner then already somewhat correct.
Otherwise, the use of a schooner wg was also in the mattress guide. "Prevents mold and mildew" recommended.
All in all I am satisfied with the thing
