Good observation and you are correct, the over generous play in the hinges allows the segments to roll more.
Since this thread died, I have continued testing. I have built ten swimbaits and tested numerous variations/combinations and nine hinge variations. I have even designed a new hinge. Still, the goal of building a swimbait with zero head shake and zero roll eludes me, but I am getting close.
The single jointed rear segment does give a false representation of the amount of roll, but the roll forces are there, otherwise it wouldn't flop from side to side. I have since changed the body design to incorporate two hinges in the rear joint. This reduced the appearance of the roll, but it is still there.
I have more ideas that I want to test, but to be honest, I got tired of having to carve the bodies. It takes 90 minutes to prepare and carve each body and this became tiresome, knowing that it is only going to swim up and down my test tank about 20 times and then retire.
It is doubly frustrating having a duplicator machine next to were I work, but it was only designed for small cranks upto 5" length. So I have shelved the swimbait testing while I design and build a new duplicator machine, this time with a 15" length capacity and a half depth capacity of 2.6", this should cover all my future swimbait needs. Once this is built, I will be much happier to turn out a new body for an insignificant or low possibility test.
My personal goal remains to build zero roll and zero head shake. I am starting to think it may not be 100% possible, but I will get as close as I can.
Dave