...the Hawking Temperature of the horizon is inversely proportional to the width of the negative energy region. Thus because in the original design the negative energy zone is close to a Planck Length in width, thus its horizon temperature is very close to the Planck Temperature. Expand it to a metre wide and the temperature is cooler than the CMB.

Problem is the negative energy zone's width was due to the original design using the Casimir effect to create the negative energy - we don't know how to do it otherwise... as yet.

And there's no Hawking radiation if the warp vehicle remains under lightspeed, so conceivably warp drive could be used for NAFAL propulsion at incredibly high gamma factors.