I have two of the Herter's molds, checked them today, the 4G1, and 4G2, and efishnc, you may be very correct with your information about the model number last digit corresponding to hook sizes.
I thought that I had used 2/0 hooks, and it appears I did, with the molds I have. So, 4/0 for the 4G4 is probably the correct call, but possibly 5/0 would fit too.
Shaunm81, I am in total agreement to with what efishnc has said about application versus design. I use saltwater designs in freshwater and vice versus, and various lures and flies intended for specific fish species, for many other species that many folks wouldn't even consider using them for.
Fish don't read the advertising or marketing ploys, forums. magazines, books or any of the hype that is associated with fishing tackle, so use what you feel will work.
I had mentioned previously about using the popeye jigs as a kid, and frankly, still us them. They were a lot more popular back then, because there was lesser numbers of jig designs. Those I used were dressed with either bucktail or feathers, and sometimes both, and we trolled them in fairly shallow water, and sometimes they were cast. The primary target species was Striped Bass, but other fish were caught on them as well. IMO, many jighead designs, such as the popeye are just chunks of lead on a hook. They add weight, and don't really have any unique action. But, they also provide a defined profile, which can be important if you're matching the available forage in size and shape.
The molds I have pour a small head, and lighter weights, and sometimes, in some locations, that was the key to success. We used other size bucktails too, but in other locations, so fit the jig to the location and type of fishing you plan on doing and don't be concerned about for what it may have been designed. You can use them for anything you choose to use them to target within reasonable limits as efishnc pointed out.
