Just a repeat of the major points raised in the previous postings.
There is nothing wrong with a rat tailed tang. As mentioned, the majority of swords are made this way. I have seen as many full tang failures, as rat tailed failures. Possibly more. Usually due, in either case, to the heat treat. A full tang may be a tad stronger, but can allow the entrance of moisture between the tang and grip. There are good points for each, and bad points for each. As mentioned, as long as the maker backs his work, then you need to go with what you want, and consider affordable at the time. A Musso "type" Bowie is not a difficult knife to make. Just takes more steel, and more time. Davy should of shown his that he made. To copy the original Musso, as close as I could was a difficult project for me, but the original has many features that can escape a simple look over, and these features all add up to the overall balance, and general feel of the knife. It is not a heavy, or clumsy knife in the hand. It is easily manuevered, and feels as good edge up, as down. It weighs only 1 lb, 12oz, which is well balanced by it's design when gripped. It would have been a formidable weapon for the time it is claimed to be from, especially for one trained with the sword. Whom ever the maker may have been, James Black as some believe, Joe Blow, or an English faker of artifacts, he either knew what he was doing, or accidentally made a great design for a large fighting knife. Either way, he did very well.