Most of the needlefish plugs you will use for heavy surf don't exactly resemble a needlefish because in real life a needlefish is skinny, sinewey and s shaped like an eel. Another example, SS makes a stubby needle, it looks more like a miniature bowling pin, but they slay the bass. The profile somewhat resembles what is out there, and they are killer for the fall.
For me it depends on how big the surf is. If it's calm you can definitely use a smaller needle, or if you want to carve something out that looks exactly like a sand eel, why not? Some sand eels get to 12" long and bigger but most will be a standard size. And the size changes with the season, one night you will have 4" sandeels and the next week they will be 7". That's why you're good with something that fits the mid range of the bait profile. If the sandeels are real small use a small sluggo and bite the head off.