I found some thin plastic tubing that worked a shim and press fit into the props, then epoxied them on to the pump shafts after filling the pump shaft recess with grease and covering it with a thin plastic disc.
Circuit Board -I can make you these relay boards (holds 8 relays) for $50 each.
If you want to make your own I've included the artwork in negative for use with the dry film photo resist process. This board would need two jumpers on the two pairs of relay/motor outputs that are end to end (+ to - and - to +) >> only one can be 'on' at a time.
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