My DA told me that daggers are at right angles blade to handle. Someone else (not a lawyer but someone who talked to one) said it wouldn't qualify as a knuckle because the handle is not for hitting. However, that's just one DA and one person's interp. Of course, I am not a lawyer, and disclaim this as being legal advice. Any interp is possible. My DA might be more inclined to tell me that because we are close and he knows this knife project is important to me. He's also told me which laws to disregard because of very low risk I'd ever be prosecuted for them in a defensive situation. But I'm a femme type so that's a big context diff.
Esav you are correct in that I originally designed the blade-inline-version (HideAway Sting and Ankle Claw) for Germans. However the ironic thing is that more Americans and Canadians are ordering it then Germans because of fma-ish reasons I guess. I've sent a lot of the regular ones to Germany, and never had one held up at customs.
If you're concerned about getting an angled bladed knife, but still want positive retention and the hands-free attribute, you could get the HideAway Sting and Ankle Claw. This version also good for concealing in very narrow places.
I think you should use whatever edge you feel confident with based on experimentation and testing under stress and thinking about different situations you could be in.
Here are the HideAways that Esav was referring to:
HideAway Sting and Ankle claw by Mick Strider:
MrFB04's Sting by Ken Brock:
TonyCCW's Sting by Mickey Yurco:
FrontSight