Hi RC and welcome to the forum.
IMO, the helicoil stretches the cam column and could weaken it where it doesn't have a lot of excess strength. I've had pretty good luck with epoxy. It doesn't form a strong bond with polyethylene but seems to stick well enough for this application.
I recommend cleaning the cam columns first with a bottle brush and making sure they are thoroughly dry. There is not a lot of excess space in the column so it doesn't take much epoxy. If you use too much it will ooze out the top of the column and can lock the cam knob.
I prefer slow set epoxy, as it allows plenty of time to insert and adjust the height of the cam knobs for a good locking position (about 180 degrees of turn or less). This is especially true if you're doing this in the sun where the internal heat can set off the mix pretty fast.
If some epoxy oozes up to the surface and interferes with the free rotation of the cam knob, you can rotate the knob every few minutes or so to break the bond before it gains any strength, until it's no longer a problem.
I did this last year and nothing has moved out of position since.