Hi Jon- Thanks for your question about your minor centipede problem. I really think you have done everything you can and actually should be glad to see a tiny one now and then because it shows you have a healthy environment. Iowa State Extension has some further information about house centipedes:

"Though house centipedes are frequently trapped in the bathtub, sink
or lavatory, that is not where they originate. Centipedes live and grow
in damp, secluded portions of basements, closets, bathrooms, unexcavated
areas under the house and beneath the bark of firewood stored indoors.
They feed on small insects and on spiders. Thus they are beneficial,
though most homeowners have a different opinion and consider them a
nuisance. The house centipede is harmless to people.

If house centipedes are too abundant for comfort, dry up and vacuum
clean, as much as possible, the areas that serve as habitat and food
source for centipedes. These are the darkest, hardest to reach areas of
the house such as under shelves, behind stored boxes, behind the washing
machine and so forth. Residual insecticides for indoor insect control
can be used, but the benefit will be little to none."

When I do find them in my own bathtub, I just scoop them up in a cup and put them back outside where they become part of the food chain again.

Hope that helps,