Yeah, its a bit tedious... but it's a just a matter of coring the bait like you would for a line-thru swimbait.
Here was my first attempt... (crude but it got things started).

This was my second attempt... the ribs are distracting to the inner pattern and also the body seems a bit too thick for good light transmission.

Changing core color to see if it makes any difference

Back to the shad body and a herring-bone pattern... (now I can smell the victory)
