Your device could trap the hummer's tongue between the ball and the end of the tube.

The tubes you are using are vacuum tubes. You need to completely fill the feeder with nectar and then install the tube. It works like putting your finger on the end of a straw to hold the liquid in. If any air is in the feeder it will leak.

they will never feed from them

the steel balls will need an inward force to get any sugar water to flow out, but the size and mass of the hummingbird will never move the ball.

the most they will ever do with it is maybe taste it once,

I hate leaky feeders. The cup type feeder with slits seems to work best.

I am also looking for this valve.