HI Quentin dividing by 800 is reasonable for a striper because of the length /girth ratio. Some of those freshwater largemouth bass look like they have swallowed a softball.
Since the girth is being squared;dividing by a higher number than 800 like 1,000 or 1200, as you mentioned, is probably more appropriate for very girthy species,like a largemouth bass.
The striper example I gave earlier, 48 in length, and 27 in. girth is a fish I caught, measured and had weighed in officially a few years ago at 47 pounds. The formula LxGxG/800 gives an estimated weight of that fish , using those dimensions, of 44 pounds.
That's reasonably close.
If you look at the world record striper dimensions of: Official IGFA All Tackle Record: 78-pound 8-ounces
Length 53 inches, Girth 34 1/2 inches; and you use the formula LxGxG/800 on that striper, it is right on the mark.- Tom