I looked up the ZT 0808 and I can see why you’d have a problem – there’s almost no flat area to clamp onto. The Low Angle Adapter has to give up a little clamping power, just because of its design and the ZT 0808 doesn’t have any to spare.
Cliff’s suggestion to use the Tormek adapter is probably the quickest solution, but you give up a little stability, as the blade is hanging free on its pivot pin. If the knife isn’t showroom-tight, the wiggle will be a problem too.
I’d try putting a patch of thick tape on each side of the blade to add a little bit of bite to the LAA. Clamp the knife with the bolster right up against the vise, and low enough to make sure the flats are well down in the clamping area to maximize the flat-area clamping power.
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