Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:3812599.
This is probably a more expensive way to get an artificial bait, but hey - I wanted to give it a go.
This is my design of a mold for a soft bait, cast in silicone. The bait is designed to be hollow in the center (like some commercial brands) to accommodate a jig head.
The soft bait is about 3.25" and will take a 3/0 offset wide gap hook (preferred), a 3/0 offset worm hook, or up to a 1/8 oz jighead (or at least the ones I had).
<i>EDIT 12Sep19</i>
<i>For a ~2.5" soft bait, print at 76.9% scale</i>
Silicone baits can be challenging to "cheat" (hide the hook underneath the skin), so I incorporated a slot for the hook to sit.
I used the 100% silicone caulk and dish soap method. I used cooking spray as a release agent. I colored the silicone with food coloring, filled both halves of the mold, inserted the core, and pressed together. There's flashing to clean up, but it's not that bad.
Without the core, the antenna will not be separate from the body. Also, I believe the hollow body will assist in ensuring a set hook by allowing the soft bait to compress, exposing the hook.
I don't think a PLA / PETG / NYLON mold would survive hot plastisol (but I've never tried).
Prototypes were printed in PLA at a .32 layer height with a 0.4 mm nozzle. They look pretty good, so I will probably not try anything higher res.
Will it catch fish? Only time will tell.