I have tried this before and after a bit of buggering around tying little bits of FC and knots and sh1t that if you really need/want it:
a. on 3 inch just put the treble directly over the protuding jighead
b. on 4 inch ended up using a small snap swivle with treble over the protuding jighead
On each I cut a just small enough bit of plastic like off the jighead boxes they come in and put that over the hook barb and pushed down flat on the treble/swivle. This stopped it coming off of the jighead should a fish take the treble. One of the treble barbs just gets hooked into the back of the plastic to hold it there.
Don't do it very often but it does work. My 2c anyway.