Only problem with double-edged blades is that they're illegal in many states . . . including mine. Only way to get around that would be to make two versions . . . one single-edged and one double-edged. That way everybody who wanted one could get one.

By the way, that's exactly what Boker does for the AF-12. AF-12s sold in CA are single-edged.

Parts of Penal Code 12020 cover street carry of knives. It also flat bans some types.

12020. (a) Any person in this state who does any of the following is punishable by imprisonment in a county jail not exceeding one year or in the state prison:
(1) Manufactures or causes to be manufactured, imports into the state, keeps for sale, or offers or exposes for sale, or who gives, lends, or possesses...any ballistic knife...any nunchaku...any metal knuckles, any belt buckle knife, any leaded cane, any zip gun, any shuriken [ed: "throwing star"]...any lipstick case knife, any cane sword, any shobi-zue, any air gauge knife, any writing pen knife, any metal military practice handgrenade or metal replica handgrenade, or any instrument or weapon of the kind commonly known as a blackjack, slungshot, billy, sandclub, sap, or sandbag. [Ed. Note: this is the paragraph covering "what you cannot own at all" - some of it is downright weird. Plastic/ceramic knives that can go through a metal detector are also banned somewhere in PC12020.]
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(4) Carries concealed upon his or her person any dirk or dagger.
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(24) As used in this section, a "dirk" or "dagger" means a knife or other instrument with or without a handguard that is capable of ready use as a stabbing weapon that may inflict great bodily injury or death. A nonlocking folding knife, a folding knife that is not prohibited by Section 653k, or a pocketknife is capable of ready use as a stabbing weapon that may inflict great bodily injury or death only if the blade of the knife is exposed and locked into position. [Ed. note: so if it's a PC653k-legal knife, and it's carried concealed while folded, it's not "readily available" and therefore doesn't meet the "dirk or dagger definition". ONLY "dirks or daggers" need to be open-carry.]
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25(d) Knives carried in sheaths which are worn openly suspended from the waist of the wearer are not concealed within the meaning of this section.

Part 25(d) applies to "dirks or daggers" that must be open carried. It is VERY confusing in that it is an example of legal open carry, but not the only possible "recipe".

[color:"red"]Nowhere in any of this is there a length limit, or a ban on double-edge. Note the way "dirk or dagger" is completely re-defined ("readily available stabbing implement"). [/color]