Hullo & welcome to PD's John
......first the steam plant & now this little boiler feed pump with neo-magnet valve holding function

This must have been quite a bit of trial & error, as these little magnets [with varying gauss] are extremely difficult to pull apart in a
straight linear movementThis is indeed a very intelligent method of achieving ....as you have said 'a difficult challenge'
My involvement is associated with 5" Gauge engines, and their builders often note....many of their steam-driven feed pumps are problematic, and they rely on the larger axle driven pumps
Well done & happy boating under steam
Derek