Bob -
I wonder why folks can't use some super glue on the pre-drilled worms. Just a dropof super glue at each end with the line moved back and forth a time or two should result in worm held in place. Suspect such a worm would stay in place at least as long as those worms using a threader.

Might be even be better on a braided leader rather than mono.

Just a couple ideas to consider.

Tight lines
Curt