Chris's point about demeanor is probably the best advice. Picture two people at the post office, both have heavy envelopes they've just received. One is 18 and is wearing a puffy jacket and his hat on backwards. He whips out a balisong and spins it open. The other is 70 and wearing a plaid shirt. He reaches into his pocket for a Buck folder and slowly opens it with both hands. Which one do you notice and size up as a threat?

Why do you want to carry an eight inch Kabar in a downtown area? And as a 25 year old, I get "Because I want to." But what tasks can't you use a less threatening knife for? I'm an Army officer, but even in uniform, my goto knife is a Swiss Army tinker with red handles. Even though I generally carry two other knives much faster and easier to deploy. No-one, but no-one notices I carry the swiss army knife. They only ever notice when I draw one of the other two knives. Either with a "Cool, what's that?", or a "Damn sir, where'd you pull that from?" When I take out the swiss army knife, I might as well be pulling out a pen for all the notice it gets. What kind of attention do you want? And are the tasks you need that knife for worth that attention? Because a knife like that draws attention.