I'm not sure if you have used a bandsaw before but you don't need to clamp a piece down, you only need to have something in place to keep the piece from rotating (the v-block) and a stop to push the blank into the blade (plate at the back of the rear v-block). It's as secure as any workpiece fed into a bandsaw, I'm the brother in law and have used this very jig with no worries or incident.
Yes, I have a 3HP, 18" Jet... but it's difficult to tell the complete construction from the photos. From the look of it, the blank hangs off the end of the V-block set, which means a fulcrum being pulled down at one end by a cutting blade. What's preventing the blank from tipping right into the blade?