While finishing up my lit review for my research class I came across a new study.
Swinton, P., Agouris, I., Lloyd, R., Stewart, A., & Keogh, J. (2012). Effect of load positioning on the kinematics and kinetics of weighted jumps. Journal of Strength and Conditioning Research, 26(4), 906-913.
They basically wanted to see the differences in forces, velocity, and peak-RFD in standard barbell weighted jumps vs hexagonal barbell jumps. Loads were based off of 1RM of both barbell back squat and hexagonal deadlift. What they found was that hexagonal barbell jumps resulted in significant increases in peak force, peak power, and peak RFD, with trends towards higher velocity, average force, and average power values. Essentially, participants were able to jump HIGHER with HEAVIER loads when using the hexagonal barbell when compared to holding a barbell at shoulder level. They found in their study that peak power occurred at 20% 1RM hexagonal barbell.