[vega1860]

Don't think I can tie a bowline because the shackle is spliced on the end of my halyard and the shackle won't fit thru the grommet....

Good advice about carbiners spontaneously attaching to stays and lines. I got one that you secure closed with a screwing mechanism.

I'll have to look into soft shackles, not familiar with that.

But assuming I can get a metal attachment, ring, or carbiner that will not catch onto things its not supposed to, is there a downside to attaching a shackle to another metal part?

An old salt (Experienced sailor) once told me "Never put anything on the end of a sheet or halyard that you don't want slapping you in the face."

Clap a whipping on the line an inch above the splice. Cut the shackle off. Use a bowline. Problem solved.

Seriously. A metal shackle on the end of a sheet or halyard can inflict serious damage on a sailor who lets the end get away from him. The weight of that shackle in the clew of a flogging headsail could mean death or serious injury to the foredeck crew.